Glossary of Unicode Terms
This glossary is updated periodically to stay synchronized with changes to various standards maintained by the Unicode Consortium.
Translations of Unicode and ISO/IEC 10646 terminology are also available.
A
Abjad. A writing system in which only
consonants are indicated. The term “abjad” is derived from the first
four letters of the traditional order of the Arabic script: alef,
beh, jeem, dal. (See
Section 6.1, Writing Systems.)
Abstract Character.
A unit of information used for the organization, control, or
representation of textual data. (See definition D7 in
Section 3.4,
Characters and Encoding.)
Abstract Character Sequence.
An ordered sequence of one or more abstract characters. (See
definition D8 in Section
Section 3.4,
Characters and Encoding.)
Abugida. A writing system in which
consonants are indicated by the base letters that have an inherent
vowel, and in which other vowels are indicated by additional
distinguishing marks of some kind modifying the base letter. The
term “abugida” is derived from the first four letters of the
Ethiopic script in the Semitic order: alf, bet, gaml, dant. (See
Section 6.1, Writing Systems.)
Accent Mark. A
mark placed above, below, or to the side of a character to alter its
phonetic value. (See also diacritic.)
Acrophonic. Denoting letters or numbers by the first letter of their
name. For example, the Greek acrophonic numerals are variant forms
of such initial letters.
Aksara. (1) In Sanskrit grammar, the term for “letter” in general,
as opposed to consonant (vyanjana) or vowel (svara). Derived from
the first and last letters of the traditional ordering of Sanskrit
letters—“a” and “ksha”. (2) More generally, in Indic writing
systems, aksara refers to a “syllable,” consisting of a consonant
plus vowel sequence, where the vowel may or may not be the inherent
vowel of the consonant letter. When multiple consonants are
involved, the aksara represents the entire orthographic syllable,
which can include two or more leading consonants that may be
visually presented in conjunct forms; in such cases, the aksara may
not be identical to the phonological syllable.
Algorithm. A term used in a broad sense in the Unicode Standard, to
mean the logical description of a process used to achieve a
specified result. This does not require the actual procedure
described in the algorithm to be followed; any implementation is
conformant as long as the results are the same.
Alphabet. A writing system in which both consonants and vowels are
indicated. The term “alphabet” is derived from the first two letters
of the Greek script: alpha, beta. (See
Section 6.1, Writing Systems.)
Alphabetic Property. Informative property of the primary units of
alphabets and/or syllabaries. (See
Section 4.10, Letters, Alphabetic, and Ideographic.)
Alphabetic Sorting. (See
collation.)
Annotation. The association of secondary textual content with a
point or range of the primary text. (The value of a particular
annotation is considered to be a part of the “content” of the text.
Typical examples include glossing, citations, exemplification,
Japanese yomi, and so on.)
ANSI. (1) The American National Standards Institute. (2) The
Microsoft collective name for all Windows code pages. Sometimes used
specifically for code page 1252, which is a superset of ISO/IEC
8859-1.
Apparatus Criticus. Collection of conventions used by editors to
annotate and comment on text.
Arabic Digits. The term "Arabic digits"
may mean either the digits in the Arabic script (see
Arabic-Indic digits) or the
ordinary ASCII digits in contrast to Roman numerals (see
European digits). When the term
"Arabic digits" is used in Unicode specifications, it means
Arabic-Indic digits. See Terminology for Digits for additional information on terminology related to digits.
Arabic-Indic Digits. Forms of decimal digits used in most parts of the
Arabic world (for instance, U+0660, U+0661, U+0662, U+0663). Although
European digits (1, 2, 3,…)
derive historically from these forms, they are visually distinct and
are coded separately. (Arabic-Indic digits are sometimes called Indic
numerals; however, this nomenclature leads to confusion with the
digits currently used with the scripts of India.) Variant forms of Arabic-Indic digits used
chiefly in Iran and Pakistan are referred to as Eastern Arabic-Indic
digits. (See
Section 9.2, Arabic.) See Terminology for Digits for additional information on terminology related to digits.
ASCII. (1) The American Standard Code for Information Interchange, a
7-bit coded character set for information interchange. It is the
U.S. national variant of ISO/IEC 646 and is formally the U.S.
standard ANSI X3.4. It was proposed by ANSI in 1963 and finalized in
1968. (2) The set of 128 Unicode characters from U+0000 to U+007F,
including control codes as well as graphic characters. (3) ASCII has
been incorrectly used to refer to various 8-bit character encodings
that include ASCII characters in the first 128 code points.
ASCII digits. The digit characters U+0030 to U+0039. Also known as European digits. See Terminology for Digits for additional information on terminology related to digits.
Assigned Character. A code point that is assigned to an abstract character.
This refers to graphic, format, control, and private-use characters
that have been encoded in the Unicode Standard. (See
Section 2.4, Code Points and Characters.)
Assigned Code Point. (See
designated code point.)
Atomic Character. A character that is not decomposable. (See
decomposable character.)
B
Base Character. Any graphic
character except for those with the General Category of Combining
Mark (M). (See definition D51 in
Section 3.6, Combination.) In a
combining character sequence, the base character is the initial
character, which the combining marks are applied to.
Basic Multilingual Plane.
Plane 0, abbreviated as BMP.
Bicameral. A script that
distinguishes between two cases. (See case.)
Most often used in the context of Latin-based alphabets of Europe
and elsewhere in the world.
Bidi. Abbreviation of bidirectional,
in reference to mixed left-to-right and right-to-left text.
Bidirectional Display.
The process or result of mixing left-to-right text and right-to-left
text in a single line. (See
Unicode Standard
Annex #9, “Unicode Bidirectional Algorithm.”)
Big-endian. A computer
architecture that stores multiple-byte numerical values with the
most significant byte (MSB) values first.
Binary Files. Files containing
nontextual information.
Block. A grouping of characters
within the Unicode encoding space used for organizing code charts. Each block is a uniquely named, continuous, non-overlapping range of code points, containing a multiple of 16 code points, and starting at a location that is a multiple of 16. A block may contain unassigned
code points, which are reserved.
BMP. Acronym for Basic Multilingual
Plane.
BMP Character. A Unicode encoded
character having a BMP code point. (See
supplementary character.)
BMP Code Point. A Unicode code
point between U+0000 and U+FFFF. (See
supplementary code point.)
BNF. Acronym for Backus-Naur Form,
a formal meta-syntax for describing context-free syntaxes. (For
details, see
Appendix A, Notational Conventions.)
BOCU-1. Acronym for Binary Ordered
Compression for Unicode. A Unicode compression scheme that is
MIME-compatible (directly usable for e-mail) and preserves binary
order, which is useful for databases and sorted lists.
BOM. Acronym for
byte order mark.
Bopomofo. An alphabetic script used
primarily in the Republic of China (Taiwan) to write the sounds of
Mandarin Chinese and some other dialects. Each symbol corresponds to
either the syllable-initial or syllable-final sounds; it is
therefore a subsyllabic script in its primary usage. The name is
derived from the names of its first four elements. More properly
known as zhuyin zimu or zhuyin fuhao in Mandarin
Chinese.
Boustrophedon. A pattern of
writing seen in some ancient manuscripts and inscriptions, where
alternate lines of text are laid out in opposite directions, and
where right-to-left lines generally use glyphs mirrored from their
left-to-right forms. Literally, “as the ox turns,” referring to the
plowing of a field.
Braille. A writing system using a
series of raised dots to be read with the fingers by people who are
blind or whose eyesight is not sufficient for reading printed
material. (See
Section 21.1, Braille.)
Braille Pattern. One of the
64 (for six-dot Braille) or 256 (for eight-dot Braille) possible
tangible dot combinations.
Byte. (1) The minimal unit of
addressable storage for a particular computer architecture. (2) An
octet. Note that many early computer architectures used bytes larger
than 8 bits in size, but the industry has now standardized almost
uniformly on 8-bit bytes. The Unicode Standard follows the current
industry practice in equating the term byte with octet
and using the more familiar term byte in all contexts. (See
octet.)
Byte Order Mark. The Unicode
character U+FEFF when used to indicate the byte order of a text.
(See
Section 2.13, Special Characters and Noncharacters, and
Section 23.8, Specials.)
Byte Serialization. The
order of a series of bytes determined by a computer architecture.
Byte-Swapped. Reversal of the
order of a sequence of bytes.
C
Camelcase. A casing convention for compound terms or identifiers, in which the letters are mostly lowercased, but component words or abbreviations may be capitalized. For example, "ThreeWordTerm" or "threeWordTerm".
Canonical. (1) Conforming to the
general rules for encoding—that is, not compressed, compacted, or in
any other form specified by a higher protocol. (2) Characteristic of
a normative mapping and form of equivalence specified in
Chapter
3, Conformance.
Canonical Composition. A step in the algorithm for Unicode Normalization Forms, during which decomposed sequences are replaced by primary composites, where possible. (See definition D115 in
Section 3.11, Normalization Forms.)
Canonical Decomposable Character.
A character that is not identical to its canonical decomposition.
(See definition D69 in
Section 3.7. Decomposition.)
Canonical Decomposition.
Mapping to an inherently equivalent sequence—for example, mapping ä
to a + combining umlaut. (For a full, formal definition, see definition D68 in
Section 3.7. Decomposition.)
Canonical Equivalent.
Two character sequences are said to be canonical equivalents if
their full canonical decompositions are identical. (See definition
D70 in
Section 3.7. Decomposition.)
Cantillation Mark. A mark
that is used to indicate how a text is to be chanted or sung.
Capital Letter. Synonym for
uppercase letter. (See case.)
Case. (1) Feature of certain
alphabets where the letters have two distinct forms. These variants,
which may differ markedly in shape and size, are called the
uppercase letter (also known as capital or majuscule) and the
lowercase letter (also known as small or minuscule). (2) Normative
property of characters, consisting of uppercase, lowercase, and titlecase (Lu, Ll, and Lt). (See
Section 4.2, Case.)
Case Mapping. The association of
the uppercase, lowercase, and titlecase forms of a letter. (See
Section 5.18, Case Mappings.)
Case-Ignorable. A character C is defined to be case-ignorable if C has the value MidLetter (ML), MidNumLet (MB), or Single_Quote (SQ) for the Word_Break property or its General_Category is one of Nonspacing_Mark (Mn), Enclosing_Mark (Me), Format (Cf), Modifier_Letter (Lm), or Modifier_Symbol (Sk). (See definition D136 in
Section 3.13, Default Case Algorithms.)
Case-Ignorable Sequence. A sequence of zero or more case-ignorable
characters. (See definition D137 in
Section 3.13, Default Case Algorithms.)
CCS. (1) Acronym for
coded character set. (2) Also used as an acronym for
combining character sequence.
Cedilla. A mark originally placed
beneath the letter c in French, Portuguese, and Spanish to indicate
that the letter is to be pronounced as an s, as in façade.
Obsolete Spanish diminutive of ceda, the letter z.
CEF. Acronym for
character encoding form.
CES. Acronym for
character encoding scheme.
Character. (1) The smallest
component of written language that has semantic value; refers to the
abstract meaning and/or shape, rather than a specific shape (see
also glyph), though in code tables some form of visual
representation is essential for the reader’s understanding. (2)
Synonym for abstract character. (3) The basic unit of
encoding for the Unicode character encoding. (4) The English name
for the ideographic written elements of Chinese origin. [See
ideograph (2).]
Character Block. (See
block.)
Character Class. A set of characters sharing a particular set of
properties.
Character Encoding Form.
Mapping from a character set definition to the actual code units
used to represent the data.
Character Encoding Scheme.
A character encoding form plus byte serialization. There are
seven character encoding schemes in Unicode: UTF-8, UTF-16,
UTF-16BE, UTF-16LE, UTF-32, UTF-32BE, and UTF-32LE.
Character Name. A unique string
used to identify each abstract character encoded in the standard.
(See definition D4 in
Section 3.3, Semantics.)
Character Name Alias. An additional unique string identifier, other
than the character name, associated with an encoded character in the
standard. (See definition D5 in
Section 3.3, Semantics.)
Character Properties. A
set of property names and property values associated with individual
characters. (See
Chapter
4, Character Properties.)
Character Repertoire.
The collection of characters included in a character set.
Character Sequence.
Synonym for abstract character sequence.
Character Set. A collection of
elements used to represent textual information.
Charset. (See
coded character set.)
Chillu. Abbreviation for chilaaksharam (singular) (cillakṣaram).
Refers to any of a set of sonorant consonants in Malayalam, when
appearing in syllable-final position with no inherent vowel.
Choseong. A sequence of one or more leading consonants in Korean.
Chu Hán. The name for Han characters used in Vietnam; derived from hànzì.
Chu Nôm. A demotic script of Vietnam
developed from components of Han characters. Its creators used
methods similar to those used by the Chinese in creating Han
characters.
CJK. Acronym for Chinese, Japanese, and
Korean. A variant, CJKV,
means Chinese, Japanese, Korean, and Vietnamese.
CLDR.
(See Unicode Common
Locale Data Repository.)
Coded Character. (See
encoded character.)
Coded Character Representation. Synonym for
coded character
sequence.
Coded Character Sequence.
An ordered sequence of one or more code points. Normally, this
consists of a sequence of encoded characters, but it may also
include noncharacters or reserved code points. (See
definition D12 in
Section 3.4,
Characters and Encoding.)
Coded Character Set. A
character set in which each character is assigned a numeric code
point. Frequently abbreviated as character set, charset, or
code set; the acronym CCS is also used.
Code Page. A coded character set,
often referring to a coded character set used by a personal
computer—for example, PC code page 437, the default coded character
set used by the U.S. English version of the DOS operating system.
Code Point. (1) Any value in the
Unicode codespace; that is, the range
of integers from 0 to 10FFFF16. (See definition D10 in
Section 3.4,
Characters and Encoding.) Not all code points are assigned to encoded characters. See code point type. (2) A value, or position, for a
character, in any coded character set.
Code Point Type. Any of the seven fundamental classes of code points in the standard: Graphic, Format, Control, Private-Use, Surrogate, Noncharacter, Reserved.
(See definition D10a in
Section 3.4,
Characters and Encoding.)
Code Position. Synonym for
code point. Used in ISO character encoding standards.
Code Set. (See
coded character set.)
Codespace. (1) A range of numerical values available for encoding
characters. (2) For the Unicode Standard, a range of integers from 0
to 10FFFF16. (See definition D9 in
Section 3.4,
Characters and Encoding.)
Code Unit. The minimal bit combination that can represent a unit of
encoded text for processing or interchange. The Unicode Standard
uses 8-bit code units in the UTF-8 encoding form, 16-bit code units
in the UTF-16 encoding form, and 32-bit code units in the UTF-32
encoding form. (See definition D77 in
Section 3.9, Unicode Encoding Forms.)
Code Value. Obsolete synonym for
code unit.
Collation. The process of
ordering units of textual information. Collation is usually specific
to a particular language. Also known as alphabetizing or
alphabetic sorting.
Unicode Technical
Standard #10, “Unicode Collation Algorithm," defines a complete, unambiguous, specified
ordering for all characters in the Unicode Standard.
Combining Character. A
character with the General Category of Combining Mark (M). (See
definition D52 in
Section 3.6, Combination.) (See also
nonspacing mark.)
Combining Character
Sequence. A maximal character sequence consisting of either
a base character followed by a sequence of one or more characters
where each is a combining character,
zero width joiner, or
zero width non-joiner;
or a sequence of one or more characters where each is a combining
character, zero width joiner,
or zero width non-joiner.
(See definition D56 in
Section 3.6, Combination.)
Combining Class. A numeric
value in the range 0..254 given to each Unicode code point, formally
defined as the property Canonical_Combining_Class. (See definition
D104 in
Section 3.11, Normalization Forms.)
Combining Mark. A commonly used synonym for combining character.
Compatibility. (1) Consistency with existing practice or preexisting
character encoding standards. (2) Characteristic of a normative
mapping and form of equivalence specified in
Section 3.7. Decomposition.
Compatibility Character. A character that would not have been
encoded except for compatibility and round-trip convertibility with
other standards. (See
Section 2.3, Compatibility Characters.)
Compatibility Composite Character. Synonym for
compatibility
decomposable character.
Compatibility Decomposable Character.
A character whose compatibility decomposition is not identical to
its canonical decomposition. (See definition D66 in
Section 3.7. Decomposition.)
Compatibility
Decomposition. Mapping to a roughly equivalent sequence
that may differ in style. (For a full, formal definition, see
definition D65 in
Section 3.7. Decomposition.)
Compatibility Equivalent.
Two character sequences are said to be compatibility equivalents if
their full compatibility decompositions are identical. (See
definition D67 in
Section 3.7. Decomposition.)
Compatibility Precomposed Character. Synonym for
compatibility
decomposable character.
Compatibility Variant. A character that generally can be remapped to
another character without loss of information other than formatting.
Composite Character. (See
decomposable character.)
Composite Character
Sequence. (See
combining character sequence.)
Composition Exclusion. A Canonical Decomposable Character which has the property value Composition_Exclusion=True. (Used in the definition of Unicode Normalization Forms.) (See
definition D112 in
Section 3.11, Normalization Forms.)
Conformance. Adherence to a specified set of criteria for use of a
standard. (See
Chapter
3, Conformance.)
Conjunct Form. A ligated form representing a
consonant conjunct.
Consonant Cluster. A sequence of two or more consonantal sounds.
Depending on the writing system, a consonant cluster may be
represented by a single character or by a sequence of characters.
(Contrast digraph.)
Consonant Conjunct. A sequence of two or more adjacent consonantal
letterforms, consisting of a sequence of one or more dead consonants
followed by a normal, live consonant letter. A consonant conjunct
may be ligated into a single conjunct form, or it may be represented
by graphically separable parts, such as subscripted forms of the
consonant letters. Consonant conjuncts are associated with the
Brahmi family of Indic scripts. (See
Section 12.1, Devanagari.)
Contextual Variant. A text element can have a presentation form that
depends on the textual context in which it is rendered. This
presentation form is known as a contextual variant.
Contributory Property. A simple property defined merely to make the statement of a rule defining a derived property more compact or general.
(See definition D35a in
Section 3.5, Properties.)
Control Codes. The 65 characters in the ranges U+0000..U+001F and
U+007F..U+009F. Also known as control characters.
Core Specification. The central part of the Unicode Standard–the portion which up until Version 5.0 was published as a separate book. Starting with Version 5.2, this part of the standard has been published online only, rather than as a book. The core specification consists of the general introduction and framework for the standard, the formal conformance requirements, many implementation guidelines, and extensive chapters providing information about all the encoded characters, organized by script or by significant classes of characters. Formally, a version of the Unicode Standard is defined by an edition of this core specification, together with the Code
Charts, Unicode
Standard Annexes and
the Unicode
Character Database.
Cursive. Writing where the letters of a word are connected.
D
Dasia. Greek term for rough breathing mark, used in polytonic Greek character names.
DBCS. Acronym for
double-byte character set.
Dead Consonant. An Indic
consonant character followed by a virama character. This
sequence indicates that the consonant has lost its inherent vowel.
(See
Section 12.1, Devanagari .)
Decimal Digits. Digits that
can be used to form decimal-radix numbers.
Decomposable Character.
A character that is equivalent to a sequence of one or more other
characters, according to the decomposition mappings found in the
Unicode Character Database, and those described in
Section 3.12, Conjoining Jamo Behavior. It may also be known as a precomposed
character or a composite character. (See definition D63 in
Section 3.7. Decomposition.)
Decomposition. (1) The process
of separating or analyzing a text element into component units.
These component units may not have any functional status, but may be
simply formal units—that is, abstract shapes. (2) A sequence of one
or more characters that is equivalent to a decomposable character.
(See definition D64 in
Section 3.7. Decomposition.)
Decomposition Mapping. A
mapping from a character to a sequence of one or more characters
that is a canonical or compatibility equivalent and that is listed
in the character names list or described in
Section 3.12, Conjoining Jamo Behavior. (See definition D62 in
Section 3.7. Decomposition.)
Default Ignorable. Default ignorable code points are those that should be ignored by default in rendering unless explicitly supported. They have no visible glyph or advance width in and of themselves, although they may affect the display, positioning, or adornment of adjacent or surrounding characters.
(See
Section 5.21, Ignoring Characters in Processing.)
Defective
Combining Character Sequence. A combining character
sequence that does not start with a base character. (See definition
D57 in
Section 3.6, Combination.)
Demotic Script. (1) A script
or a form of a script used to write the vernacular or common speech
of some language community. (2) A simplified form of the ancient
Egyptian hieratic writing.
Dependent Vowel. A symbol or
sign that represents a vowel and that is attached or combined with
another symbol, usually one that represents a consonant. For
example, in writing systems based on Arabic, Hebrew, and Indic
scripts, vowels are normally represented as dependent vowel signs.
Deprecated. Of a coded character
or a character property, strongly discouraged from use. (Not the
same as obsolete.)
Deprecated Character. A
coded character whose use is strongly discouraged. Such characters
are retained in the standard, indefinitely but should not be used. (See
definition D13 in
Section 3.4,
Characters and Encoding.)
Designated Code Point.
Any code point that has either been assigned to an abstract
character (assigned characters) or that has otherwise been
given a normative function by the standard (surrogate code points
and noncharacters). This definition excludes reserved code points.
Also known as assigned code point. (See
Section 2.4 Code Points and Characters.)
Deterministic Comparison. A string comparison in which strings that do not have identical contents will compare as unequal. There are two main varieties, depending on the sense of "identical:" (a) binary equality, or (b) canonical equivalence. This is a property of the comparison mechanism, and not of the sorting algorithm. Also known as stable (or semi-stable) comparison.
Deterministic Sort. A sort algorithm which returns exactly the same output each time it is applied to the same input. This is a property of the sorting algorithm, and not of the comparison mechanism. For example, a randomized Quicksort (which picks a random element as the pivot element, for optimal performance) is not deterministic. Multiprocessor implementations of a sort algorithm may also not be deterministic.
Diacritic. (1) A mark applied or
attached to a symbol to create a new symbol that represents a
modified or new value. (2) A mark applied to a symbol irrespective
of whether it changes the value of that symbol. In the latter case,
the diacritic usually represents an independent value (for example,
an accent, tone, or some other linguistic information). Also called
diacritical mark or diacritical. (See also
combining character and
nonspacing mark.)
Diaeresis. Two horizontal dots
over a letter, as in naïve. The diaeresis is not
distinguished from the umlaut in the Unicode character
encoding. (See umlaut.)
Dialytika. Greek term for
diaeresis or trema, used in Greek character names.
Digits. (See
Arabic digits,
European digits, and
Indic digits.) See Terminology for Digits for additional information on terminology related to digits.
Digraph. A pair of signs or symbols
(two graphs), which together represent a single sound or a single
linguistic unit. The English writing system employs many digraphs
(for example, th, ch, sh, qu, and so on). The same two
symbols may not always be interpreted as a digraph (for example,
cathode versus cathouse). When three signs
are so combined, they are called a trigraph. More than three
are usually called an n-graph.
Dingbats. Typographical symbols and
ornaments.
Diphthong. A pair of vowels that
are considered a single vowel for the purpose of phonemic
distinction. One of the two vowels is more prominent than the other.
In writing systems, diphthongs are sometimes written with one symbol
and sometimes with more than one symbol (for example, with a
digraph).
Direction. (See
paragraph direction.)
Directionality Property.
A property of every graphic character that determines its horizontal
ordering as specified in
Unicode Standard
Annex #9, “Unicode Bidirectional Algorithm.” (See
Section 4.4,
Directionality.)
Display Cell. A rectangular
region on a display device within which one or more glyphs are
imaged.
Display Order. The order of
glyphs presented in text rendering. (See logical order and Section 2.2, Unicode Design Principles.)
Double-Byte Character Set.
One of a number of character sets defined for representing Chinese,
Japanese, or Korean text (for example, JIS X 0208-1990). These
character sets are often encoded in such a way as to allow
double-byte character encodings to be mixed with single-byte
character encodings. Abbreviated DBCS. (See also
multibyte character set.)
Ductility. The ability of a cursive
font to stretch or compress the connective baseline to effect text
justification.
Dynamic Composition.
Creation of composite forms such as accented letters or Hangul
syllables from a sequence of characters.
E
EBCDIC. Acronym for Extended
Binary-Coded Decimal Interchange Code. A group of coded character
sets used on mainframes that consist of 8-bit coded characters.
EBCDIC coded character sets reserve the first 64 code points (x00
to x3F) for control codes, and reserve the range x41 to xFE for graphic characters. The English
alphabetic characters are in discontinuous segments with uppercase
at xC1 to xC9, xD1 to xD9, xE2 to xE9, and lowercase at x81 to x89,
x91 to x99, xA2 to xA9.
ECCS. Acronym for
extended combining character sequence.
EGC. Acronym for
extended grapheme cluster.
Embedding. A concept relevant to
bidirectional behavior. (See
Unicode Standard
Annex #9, “Unicode Bidirectional Algorithm,” for detailed terminology and definitions.)
Emoji. (1) The Japanese word for "pictograph." (2) Certain pictographic and other symbols encoded in the Unicode Standard that are commonly given a colorful or playful presentation when displayed on devices. Most of the emoji in Unicode were encoded for compatibility with Japanese telephone symbol sets. (3) Colorful or playful symbols which are not encoded as characters but which are widely implemented as graphics. (See pictograph.)
Emoticon. A symbol added to text to express emotional affect or reaction—for example, sadness, happiness, joking intent, sarcasm, and so forth. Emoticons are often expressed by a conventional kind of "ASCII art," using sequences
of punctuation and other symbols to portray likenesses of facial expressions. In Western contexts these are often turned sideways, as :-) to express a happy face; in East Asian contexts other conventions often portray a facial expression without turning, as ^-^. Rendering systems often recognize conventional emoticon sequences and display them as colorful or even animated glyphs in text. There is also a set of dedicated pictographic symbols—mostly representing different facial expressions—encoded as characters in the Unicode Standard. (See pictograph.)
Encapsulated Text. (1)
Plain text surrounded by formatting information. (2) Text recoded to
pass through narrow transmission channels or to match communication
protocols.
Enclosing Mark. A nonspacing mark with the General Category of
Enclosing Mark (Me). (See definition D54 in
Section 3.6, Combination.) Enclosing marks are a subclass of nonspacing marks
that surround a base character, rather than merely being placed
over, under, or through it.
Encoded Character. An
association (or mapping) between an abstract character and a
code point. (See definition D11 in
Section 3.4,
Characters and Encoding.) By itself, an abstract character has no numerical
value, but the process of “encoding a character” associates a
particular code point with a particular abstract character, thereby
resulting in an “encoded character.”
Encoding Form. (See
character encoding form.)
Encoding Scheme. (See
character encoding scheme.)
Equivalence. In the context of
text processing, the process or result of establishing whether two
text elements are identical in some respect.
Equivalent Sequence. (See canonical equivalent.)
Escape Sequence. A sequence
of bytes that is used for code extension. The first byte in the
sequence is escape (hex 1B).
EUDC. Acronym for end-user defined character. A character defined by
an end user, using a private-use code point, to represent a
character missing in a particular character encoding. These are
common in East Asian implementations.
European Digits. Forms of
decimal digits first used in Europe and now used worldwide.
Historically, these digits were derived from the Arabic digits; they
are sometimes called “Arabic numerals,” but this nomenclature leads
to confusion with the real Arabic digits. Also called "Western digits" and "Latin digits." See Terminology for Digits for additional information on terminology related to digits.
Extended Base. Any base character, or any standard Korean syllable block. (See definition D51a in
Section 3.6, Combination.)
Extended Combining Character Sequence. A maximal character sequence consisting of either an extended base followed by a sequence of one or more characters where each is a combining character,
zero width joiner, or
zero width non-joiner; or a sequence of one or more characters where each is a combining character,
zero width joiner, or
zero width non-joiner. Abbreviated as
ECCS. (See definition D56a in
Section 3.6, Combination.)
Extended Grapheme Cluster. The text between extended grapheme cluster boundaries as specified by
Unicode Standard Annex #29, "Unicode Text Segmentation."
Abbreviated as EGC. (See definition D61 in
Section 3.6, Combination.)
F
Fancy Text. (See
rich text.)
Fixed Position Class. A subset of the range of numeric values for
combining classes—specifically, any value in the range 10..199. (See
definition D105 in
Section 3.11, Normalization Forms.)
Floating (diacritic, accent, mark). (See
nonspacing mark.)
Folding. An operation that maps similar characters to a common
target, such as uppercasing or lowercasing a string. Folding
operations are most often used to temporarily ignore certain
distinctions between characters.
Font. A collection of glyphs used for
the visual depiction of character data. A font is often associated
with a set of parameters (for example, size, posture, weight, and serifness), which, when set
to particular values, generate a collection of imagable glyphs.
Format Character. A character that is inherently invisible but that
has an effect on the surrounding characters.
Format Code. Synonym for
format character.
Formatted Text. (See
rich text.)
FSS-UTF. Acronym for File System Safe UCS Transformation Format,
published by the X/Open Company Ltd., and intended for the UNIX
environment. Now known as UTF-8.
Full Composition Exclusion. A Canonical Decomposable Character which has the property value Full_Composition_Exclusion=True.
(Used in the definition of Unicode Normalization Forms.) (See
definition D113 in
Section 3.11, Normalization Forms.)
Fullwidth. Characters of East Asian
character sets whose glyph image extends across the entire character
display cell. In legacy character sets, fullwidth characters are normally encoded in two or
three bytes. The Japanese term for fullwidth characters is zenkaku.
FVS. Acronym for Mongolian Free Variation Selector.
G
G11n. (See globalization.)
GC. 1. Acronym for
grapheme cluster. 2. Short name for the General_Category property, usually lowercased: gc.
GCGID. Acronym for Graphic Character
Global Identifier. These are listed in the IBM document Character
Data Representation Architecture, Level 1, Registry SC09-1391.
General Category. Partition
of the characters into major classes such as letters, punctuation,
and symbols, and further subclasses for each of the major classes.
(See
Section 4.5, General Category.)
Generative. Synonym for
productive.
Globalization. (1) The overall process for internationalization and localization of software products. (2) a synonym for internationalization. Also known by the abbreviation "g11n". Note that the meaning of "globalization" which is
relevant to software products should be distinguished from the more widespread use of "globalization" in the context of economics. (See internationalization, localization.)
Glyph. (1) An abstract form that
represents one or more glyph images. (2) A synonym for
glyph image. In displaying Unicode
character data, one or more glyphs may be selected to depict a
particular character. These glyphs are selected by a rendering
engine during composition and layout processing. (See also
character.)
Glyph Code. A numeric code that
refers to a glyph. Usually, the glyphs contained in a font are
referenced by their glyph code. Glyph codes may be local to a
particular font; that is, a different font containing the same
glyphs may use different codes.
Glyph Identifier. Similar to
a glyph code, a glyph identifier is a label used to refer to a glyph
within a font. A font may employ both local and global glyph
identifiers.
Glyph Image. The actual, concrete
image of a glyph representation having been rasterized or otherwise
imaged onto some display surface.
Glyph Metrics. A collection of
properties that specify the relative size and positioning along with
other features of a glyph.
Grapheme. (1) A minimally
distinctive unit of writing in the context of a particular writing
system. For example, ‹b› and ‹d› are distinct graphemes in English
writing systems because there exist distinct words like big and dig.
Conversely, a lowercase italiform letter a and a
lowercase Roman letter a are not distinct graphemes because no word
is distinguished on the basis of these two different forms. (2) What
a user thinks of as a character.
Grapheme Base. A character
with the property Grapheme_Base, or any standard Korean syllable
block. (See definition D58 in
Section 3.6, Combination.)
Grapheme Cluster. The text between grapheme cluster boundaries as specified by
Unicode Standard Annex #29, "Unicode Text Segmentation." (See definition D60 in
Section 3.6, Combination.) A grapheme cluster represents a horizontally segmentable unit of text, consisting of some grapheme base (which may consist of a Korean syllable) together with any number of nonspacing marks applied to it.
Grapheme Extender. A
character with the property Grapheme_Extend. (See definition D59 in
Section 3.6, Combination.) Grapheme extender characters consist of
all nonspacing marks, zero
width joiner, zero
width non-joiner, and a small number of spacing marks.
Graphic Character. A
character with the General Category of Letter (L), Combining Mark
(M), Number (N), Punctuation (P), Symbol (S), or Space Separator
(Zs). (See definition D50 in
Section 3.6. Combination.)
Guillemet. Punctuation marks
resembling small less-than and greater-than signs, used as quotation
marks in French and other languages. (See “Language-Based Usage of
Quotation Marks” in
Section 6.2, General Punctuation.)
H
Halant. A preferred Hindi synonym
for a virama. It literally means killer, referring to
its function of killing the inherent vowel of a consonant
letter. (See
virama.)
Half-Consonant Form. In
the Devanagari script and certain other scripts of the Brahmi family
of Indic scripts, a dead consonant may be depicted in the so-called
half-form. This form is composed of the distinctive part of a
consonant letter symbol without its vertical stem. It may be used to
create conjunct forms that follow a horizontal layout pattern. Also
known as half-form.
Halfwidth. Characters of East Asian
character sets whose glyph image occupies half of the character
display cell. In legacy character sets, halfwidth characters are
normally encoded in a single byte. The Japanese term for halfwidth characters is hankaku.
Han Characters. Ideographic
characters of Chinese origin. (See
Section 18.1, Han.)
Hangul. The name of the script used to
write the Korean language.
Hangul Syllable. (1) Any of
the 11,172 encoded characters of the Hangul Syllables character
block, U+AC00..U+D7A3. Also called a precomposed Hangul syllable
to clearly distinguish it from a Korean syllable block. (2) Loosely
speaking, a Korean syllable block.
Hanja. The Korean name for Han
characters; derived from the Chinese word hànzì.
Hankaku. (See
halfwidth.)
Han Unification. The process
of identifying Han characters that are in common among the writing
systems of Chinese, Japanese, Korean, and Vietnamese.
Hànzì. The Mandarin Chinese name
for Han characters.
Harakat. Marks that indicate vowels
or other modifications of consonant letters in Arabic script.
Hasant. The Bangla name for halant. (See
virama.)
Higher-Level Protocol.
Any agreement on the interpretation of Unicode characters that
extends beyond the scope of this standard. Note that such an
agreement need not be formally announced in data; it may be implicit
in the context. (See definition D16 in
Section 3.4,
Characters and Encoding.)
High-Surrogate Code Point.
A Unicode code point in the range U+D800 to U+DBFF. (See definition
D71 in
Section 3.8, Surrogates.)
High-Surrogate Code Unit.
A 16-bit code unit in the range D80016 to DBFF16,
used in UTF-16 as the leading code unit of a surrogate pair. Also
known as a leading surrogate. (See definition D72 in
Section 3.8, Surrogates.)
Hiragana. One of two standard
syllabaries associated with the Japanese writing system. Hiragana
syllables are typically used in the representation of native
Japanese words and grammatical particles.
HTML. HyperText Markup Language. A text
description language related to SGML; it mixes text format markup
with plain text content to describe formatted text. HTML is
ubiquitous as the source language for Web pages on the Internet.
Starting with HTML 4.0, the Unicode Standard functions as the
reference character set for HTML content. (See also
SGML.)
I
I18n. (See internationalization.)
IANA. Acronym for Internet Assigned
Numbers Authority.
ICU. Acronym for International Components for Unicode, an Open
Source set of C/C++ and Java libraries for Unicode and software
internationalization support. For information, see
http://www.icu-project.org/
Ideograph (or ideogram). (1) Any symbol that primarily denotes an idea or concept in contrast to a sound or pronunciation—for example, ♻, which denotes the concept of recycling by a series of bent arrows. (2) A generic term for the unit of writing of a logosyllabic writing system. In this sense, ideograph (or ideogram) is not systematically distinguished from logograph (or logogram). (3) A term commonly used to refer specifically to Han characters, equivalent to the Chinese, Japanese, or Korean terms also sometimes used: hànzì, kanji, or hanja. (See logograph, pictograph, sinogram.)
Ideographic Property.
Informative property of characters that are ideographs. (See
Section 4.10, Letters, Alphabetic, and Ideographic.)
Ideographic Variation Sequence. A variation sequence registered in the Ideographic Variation Database. The registration of ideographic variation sequences is subject to the rules specified in Unicode Technical Standard #37, "Unicode Ideographic Variation Database." The base character for an ideographic variation sequence must be an ideographic character, and it makes use of a variation selector in the range U+E0100..U+E01EF. The term ideographic variation sequence is sometimes abbreviated as "IVS".
IICore. A subset of common-use CJK unified ideographs, defined as
the fixed collection 370 IICore in ISO/IEC 10646. This subset
contains 9,810 ideographs and is intended for common use in East
Asian contexts, particularly for small devices that cannot support
the full range of CJK unified ideographs encoded in the Unicode
Standard.
Ill-Formed Code Unit Sequence.
A code unit sequence that does not follow the specification of a
Unicode encoding form. (See definition D84 in
Section 3.9, Unicode Encoding Forms.)
Ill-Formed Code Unit Subsequence. A non-empty subsequence of a Unicode code unit sequence X which does not contain any code units which also belong to any minimal well-formed subsequence of X. (See definition D84a in
Section 3.9, Unicode Encoding Forms.)
In-Band. An in-band channel conveys
information about text by embedding that information within the text
itself, with special syntax to distinguish it. In-band information
is encoded in the same character set as the text, and is
interspersed with and carried along with the text data. Examples are
XML and HTML markup.
Independent Vowel. In Indic
scripts, certain vowels are depicted using independent letter
symbols that stand on their own. This is often true when a word
starts with a vowel or a word consists of only a vowel.
Indic Digits. Forms of decimal
digits used in various Indic scripts (for example, Devanagari: U+0966, U+0967, U+0968, U+0969).
Arabic digits (and, eventually, European digits) derive historically
from these forms. See Terminology for Digits for additional information on terminology related to digits.
Informative. Information in this
standard that is not normative but that contributes to the correct
use and implementation of the standard.
Inherent Vowel. In writing
systems based on a script in the Brahmi
family of Indic scripts, a consonant letter symbol normally has an
inherent vowel, unless otherwise indicated. The phonetic value of
this vowel differs among the various languages written with these
writing systems. An inherent vowel is overridden either by
indicating another vowel with an explicit vowel sign or by using
virama to create a dead consonant.
Inner Caps. Mixed case format
where an uppercase letter is in a position other than first in the
word—for example, “G” in the Name “McGowan.”
Internationalization. The process of designing and implementing a software product so that it can be easily localized, with few if any structural changes. Ideally, an internationalized software product can be localized simply by translating messages and other text displayed to a user, and by adapting icons and other visual elements. An "internationalized" software product is also known as a "localizable" product. Also known by the abbreviation "i18n" and the term "World-Readiness". (See localization, globalization.)
IPA. (1) The International Phonetic
Alphabet. (2) The International Phonetic Association, which defines
and maintains the International Phonetic Alphabet.
IRG. Acronym for Ideographic Research Group, a subgroup of ISO/IEC
JTC1/SC2/WG2. (See
Appendix E, Han Unification History.)
ISCII. Acronym for Indian Script Code for Information Interchange.
J
Jamo. The Korean name for a single
letter of the Hangul script.
Jamos are used to form Hangul syllables.
Joiner. An invisible character that
affects the joining behavior of surrounding characters. (See
Section 9.2, Arabic, and “Cursive Connection” in
Section 23.2, Layout Controls.)
Jongseong. A sequence of one or
more trailing consonants in Korean.
JTC1. The Joint Technical Committee 1 of
the International Organization for Standardization and the
International Electrotechnical Commission responsible for
information technology standardization.
Jungseong. A sequence of one or
more vowels in Korean.
K
Kana. The name of a primarily syllabic script used by the Japanese
writing system. It comes in two forms, hiragana and
katakana. The
former is used to write particles, grammatical affixes, and words
that have no
kanji form; the latter is used primarily to write
foreign words.
Kanji. The Japanese name for Han characters; derived from the
Chinese word hànzì. Also romanized as
kanzi.
Katakana. One of two standard syllabaries associated with the
Japanese writing system. Katakana syllables are typically used in
representation of borrowed vocabulary (other than that of Chinese
origin), sound-symbolic interjections, or phonetic representation of
“difficult” kanji characters in Japanese.
Kerning. (1) Changing the space between certain pairs of letters to
improve the appearance of the text. (2) The process of mapping from
pairs of glyphs to a positioning offset used to change the space
between letters.
Korean Syllable Block.
A sequence of Korean jamos, consisting of one or more leading
consonants followed by one or more vowels followed by zero or more
trailing consonants, or any canonically equivalent sequence
including a precomposed Hangul syllable. In regular expression
notation: L L* V V* T*. Also called a standard
Korean syllable block. (See
Section 3.12, Conjoining Jamo Behavior.)
L
L10n. (See localization.)
LDML. (See Unicode
Locale Data Markup
Language.)
Leading Consonant. (1) In Korean, a jamo character with the
Hangul_Syllable_Type property value Leading_Jamo (in the range
U+1100..U+1159 or U+115F hangul choseong filler). Abbreviated as
L. (See definition D122 in
Section 3.12, Conjoining Jamo Behavior.) (2)
Any initial consonant in a syllable.
Leading Surrogate. Synonym for
high-surrogate code unit.
Letter. (1) An element of an alphabet. In a broad sense, it includes
elements of syllabaries and ideographs. (2) Informative property of
characters that are used to write words.
Ligature. A glyph representing a combination of two or more
characters. In the Latin script, there are only a few in modern use,
such as the ligatures between “f” and “i” or “f” and “l”. Other scripts make use of many ligatures, depending on the font
and style.
Little-endian. A computer architecture that stores multiple-byte
numerical values with the least significant byte (LSB) values first.
Localization. (1) The process of adapting a software product to use the languages and conventions suitable for a local market, such as adapting an English US software product to work in Spanish for Argentina. (2) The management of software product translation, which includes extraction of translatable text, management of translations, and generation of language resource modules. Also known by the abbreviation "L10n". Localization produces "localized" software products. (See internationalization, globalization.)
Logical Order. The order in
which text is stored in the memory representation. For the most part, logical order
corresponds to the typing order and the phonetic order. (See display order and
Section 2.2, Unicode Design Principles.)
Logical Store. Memory representation.
Logograph (or logogram). (1) Any symbol that primarily represents a word (or morpheme) in contrast to a sound or pronunciation. (2) A generic term for the unit of writing of a logosyllabic writing system. In this sense, logograph (or logogram) is not systematically distinguished from ideograph (or ideogram). (See ideograph, pictograph.)
Logosyllabary. A writing system in which the units are used
primarily to write words and/or morphemes of words, with some
subsidiary usage to represent just syllabic sounds. The best example
is the Han script.
Lowercase. (See
case.)
Low-Surrogate Code Point..
A Unicode code point in the range U+DC00 to U+DFFF. (See definition
D73 in
Section 3.8, Surrogates.)
Low-Surrogate Code Unit.
A 16-bit code unit in the range DC0016 to DFFF16, used in UTF-16 as
the trailing code unit of a surrogate pair. Also known as a trailing
surrogate. (See definition D74 in
Section 3.8, Surrogates.)
LSB. Acronym for least significant
byte.
LZW. Acronym for Lempel-Ziv-Welch,
a standard algorithm widely used for compression of data.
M
Majuscule. Synonym for uppercase. (See case.)
Mathematical Property. Informative property of characters that are
used as operators in mathematical formulae.
Matra. A dependent vowel in an Indic script. It is the name for
vowel letters that follow consonant letters in logical order. A
matra often has a completely different letterform from that for the
same phonological vowel used as an independent letter.
MBCS. Abbreviation for
multibyte character set.
MIME. Multipurpose Internet Mail Extensions. MIME is a standard that
allows the embedding of arbitrary documents and other binary data of
known types (images, sound, video, and so on) into e-mail handled by
ordinary Internet electronic mail interchange protocols.
Minimal Well-Formed Code Unit Subsequence. A well-formed Unicode code unit sequence that maps to a single Unicode scalar value. (See definition D85a in
Section 3.9, Unicode Encoding Forms.)
Minuscule. Synonym for lowercase. (See case.)
Mirrored Property. The
property of characters whose images are mirrored horizontally in
text that is laid out from right to left (versus from left to
right). (See
Section 4.7, Bidi Mirrored.)
Missing Glyph. (See
replacement glyph.)
Modifier Letter. A character
with the Lm General Category in the Unicode Character Database.
Modifier letters, which look like letters or punctuation, modify the
pronunciation of other letters (similar to diacritics). (See
Section 7.8, Modifier Letters.)
Mongolian Free Variation Selector. A subset of variation selectors, encoded in the range U+180B..U+180D, which are used specifically for the definition of standardized variation sequences for the Mongolian script. A Mongolian free variation selector always takes a Mongolian letter as its base, but is otherwise not architecturally distinct from the general-purpose variation selectors. Commonly abbreviated FVS1, FVS2, and FVS3.
Mongolian Variation Sequence. A standardized variation sequence which has a Mongolian letter as its base character. All of the currently defined Mongolian variation sequences use the Mongolian free variation selectors in the range U+180B..U+180D, but no architectural constraint prevents such sequences from also using general-purpose variation selector characters in the range U+FE00..U+FE0D. Mongolian variation sequences are unusual in that many specify a positional context (for example, initial, medial, or final) for their use, as well as a particular glyph presentation.
Monotonic. Modern Greek written with the basic accent, the
tonos.
Mora. A phonological term: the unit of
sound which determines syllable weight in some languages. Some
syllabaries have characteristics which reflect moraic structure more
or less exactly. In particular, the Japanese kana syllabaries
actually write one character per mora, rather than one character per
syllable. The Vai syllabary also counts final nasals as distinct
moras, and writes moras instead of syllables.
MSB. Acronym for most significant byte.
Multibyte Character Set. A character set encoded with a variable
number of bytes per character, often abbreviated as MBCS. Many large
character sets have been defined as MBCS so as to keep strict
compatibility with the ASCII subset and/or ISO/IEC 2022.
N
Named Unicode Algorithm.
A Unicode algorithm that is specified in the Unicode Standard or in
other standards published by the Unicode Consortium and that is
given an explicit name for ease of reference. (See definition D18 in
Section 3.4,
Characters and Encoding. See also Table 3-1, “Named
Unicode Algorithms,” for a list of named Unicode algorithms.)
Namespace. (1) A set of names, no
two of which are identical. (2) A set of names together with name
matching rules, so that all names are distinct under the matching
rules. (See definition D6 in
Section 3.3, Semantics.) Character
names are distinct if they do not match under the name matching
rules in effect for the standard.
Nekudot. Marks that indicate vowels or other modifications of
consonantal letters in Hebrew.
Neutral Character. A character that can be written either right to
left or left to right, depending on context. (See
Unicode Standard
Annex #9, “Unicode Bidirectional Algorithm.”)
NFC. (See Normalization Form C.)
NFD. (See Normalization Form D.)
NFKC. (See Normalization Form KC.)
NFKD. (See Normalization Form KD.)
Noncharacter. A code point that
is permanently reserved for internal use. Noncharacters consist of the values U+nFFFE and
U+nFFFF (where n is from 0 to 1016), and
the values U+FDD0..U+FDEF. See the FAQ on Private-Use Characters, Noncharacters and Sentinels.
Non-joiner. An invisible character
that affects the joining behavior of surrounding characters. (See
Section 9.2, Arabic, and “Cursive Connection” in
Section 23.2, Layout Controls.)
Non-overridable. A characteristic of a Unicode character property
that cannot be changed by a higher-level protocol.
Nonspacing Diacritic. A diacritic that is a nonspacing mark.
Nonspacing Mark. A combining
character with the General Category of Nonspacing Mark (Mn) or
Enclosing Mark (Me). (See definition D53 in
Section 3.6, Combination.) The position of a nonspacing mark in presentation
depends on its base character. It generally does not consume space
along the visual baseline in and of itself. (See also
combining character.)
Non-starter Decomposition. A canonical decomposition mapping to a sequence of more than one character, for which the first character in that sequence is not a Starter.
(Used in the definition of Unicode Normalization Forms.) (See
definition D111 in
Section 3.11, Normalization Forms.)
Normalization. A process of
removing alternate representations of equivalent sequences from
textual data, to convert the data into a form that can be
binary-compared for equivalence. In the Unicode Standard,
normalization refers specifically to processing to ensure that
canonical-equivalent (and/or compatibility-equivalent) strings have
unique representations. For more information, see “Equivalent
Sequences” in
Section 2.2, Unicode Design Principles, and
Section 3.11, Normalization Forms.
Normalization Form. One of the four Unicode normalization forms
defined in
Section 3.11, Normalization Forms—namely, NFC, NFD, NFKC, and NFKD.
For more information and examples, see Section 1.1, Canonical and
Compatibility Equivalence in
Unicode Standard Annex #15, "Unicode Normalization Forms."
Normalization Form C (NFC).
A normalization form that erases any canonical differences, and
generally produces a composed result. For example, a + umlaut is
converted to ä in this form. This form most closely matches legacy
usage. The formal definition
is D120 in
Section 3.11, Normalization Forms.
Normalization Form D (NFD).
A normalization form that erases any canonical differences, and
produces a decomposed result. For example, ä is converted to a +
umlaut in this form. This form is most often used in internal
processing, such as in collation. The
formal definition is D118 in
Section 3.11, Normalization Forms.
Normalization Form KC (NFKC).
A normalization form that erases both canonical and compatibility
differences, and generally produces a composed result: for example,
the single dž character is converted to d + ž in this form. This form
is commonly used in matching. The
formal definition is D121 in
Section 3.11, Normalization Forms.
Normalization Form KD (NFKD).
A normalization form that erases both canonical and compatibility
differences, and produces a decomposed result: for example, the
single dž character is converted to d + z + caron in this form. The
formal definition is D119 in
Section 3.11, Normalization Forms.
Normative. Required for conformance with the Unicode Standard.
NSM. Acronym for
nonspacing mark.
Numeric Value Property.
A property of characters used to represent numbers. (See
Section 4.6, Numeric Value.)
O
Obsolete. Applies to a character that is no longer in current use,
but that has been used historically. Whether a character is obsolete
depends on context: For example, the Cyrillic letter big yus is
obsolete for Russian, but is used in modern Bulgarian. (Not the same
as
deprecated.)
Octet. An ordered sequence of eight bits considered as a unit. The
Unicode Standard follows current industry practice in referring to
an octet as a byte. (See byte.)
Out-of-Band. An out-of-band channel conveys additional information
about text in such a way that the textual content, as encoded, is
completely untouched and unmodified. This is typically done by
separate data structures that point into the text.
Overridable. A characteristic of a Unicode character property that
may be changed by a higher-level protocol to create desired
implementation effects.
Oxia. Greek term for acute accent, used in polytonic Greek character names.
P-Q
Paragraph Direction. The default direction (left or
right) of the
text of a paragraph. This direction does not change the display
order of characters within an Arabic or English word. However, it
does change the display order of adjacent Arabic and English words,
and the display order of neutral characters, such as punctuation and
spaces. For more details, see
Unicode Standard Annex #9, “Unicode
Bidirectional Algorithm,” especially definitions BD2–BD5.
Paragraph Embedding Level.
The embedding level that determines the default bidirectional
orientation of the text in that paragraph.
Perispomeni. Greek term for circumflex accent, used in polytonic Greek character names.
Phoneme. A minimally distinct sound in the context of a particular
spoken language. For example, in American English, /p/ and /b/ are
distinct phonemes because pat and bat are distinct; however, the two
different sounds of /t/ in tick and stick are not distinct in
English, even though they are distinct in other languages such as
Thai.
Pictograph (or pictogram). Any symbol that denotes an object by means of a more or less conventional visual likeness—for example, ✈. (See emoji, ideograph, logograph.)
Pinyin. Standard system for the romanization of Chinese on the basis
of Mandarin pronunciation.
Pivot Conversion. The use of a third character encoding to serve as
an intermediate step in the conversion between two other character
encodings. The Unicode Standard is widely used to support pivot
conversion, as its character repertoire is a superset of most other
coded character sets.
Plain Text. Computer-encoded text that consists
only of a sequence
of code points from a given standard, with no other formatting or
structural information. Plain text interchange is commonly used
between computer systems that do not share higher-level protocols.
(See also rich text.)
Plane. A range of 65,536 (1000016)
contiguous Unicode code points, where the first code point is an
integer multiple of 65,536 (1000016). Planes are numbered
from 0 to 16, with the number being the first code point of the
plane divided by 65,536. Thus Plane 0 is U+0000..U+FFFF, Plane 1 is
U+10000..U+1FFFF, ..., and Plane 16 (1016)
is U+100000..10FFFF. (Note that ISO/IEC 10646 uses
hexadecimal notation for the plane numbers—for example, Plane B instead of
Plane 11). (See Basic
Multilingual Plane and supplementary
planes.)
Points. (1) The nonspacing vowels and other signs of written Hebrew.
(2) A unit of measurement in typography.
Polytonic. Ancient Greek written with several contrastive accents.
Precomposed Character. (See decomposable character.)
Presentation Form. A ligature or variant glyph that has been encoded
as a character for compatibility. (See also
compatibility character
(1).)
Primary Composite. A
Canonical Decomposable Character which is not a Full Composition Exclusion. (Used in
the definition of Unicode Normalization Forms.) (See definition D114
in
Section 3.11, Normalization Forms.)
Private Use. Refers to designated code points in the Unicode
Standard or other character encoding standards whose interpretations
are not specified in those standards and whose use may be determined
by private agreement among cooperating users.
Private Use Area (PUA). Any
one of the three blocks of private-use code points in the Unicode
Standard.
Private-Use Code Point.
Code points in the ranges U+E000..U+F8FF, U+F0000..U+FFFFD, and
U+100000..U+10FFFD. (See definition D49 in
Section 3.5, Properties.) These code points are designated in the
Unicode Standard for private use.
Productive. Said of a feature or
rule that can be employed in novel combinations or circumstances,
rather than being restricted to a fixed list. In the Unicode
Standard, combining marks—particularly the accents—are productive.
In contrast, variation selectors are deliberately not productive.
Also known as
generative.
Property. (See
character properties.)
Property Alias. A unique
identifier for a particular Unicode character property. (See
definition D47 in
Section 3.5, Properties.)
Property Value Alias. A
unique identifier for a particular enumerated value for a particular
Unicode character property. (See definition D48 in
Section 3.5, Properties.)
Prosgegrammeni. Greek term for adscript iota, used in polytonic Greek character names.
Provisional. A property or feature that is unapproved and tentative,
and that may be incomplete or otherwise not in a usable state.
Psili. Greek term for smooth breathing mark, used in polytonic Greek character names.
PUA. Acronym for Private Use Area.
Pulli. The Tamil name for virama. (See
virama.)
R
Radical. A structural component of a Han character conventionally
used for indexing. The traditional number of such radicals is 214.
Rendering. (1) The process of selecting and laying out glyphs for
the purpose of depicting characters. (2) The process of making
glyphs visible on a display device.
Repertoire. (See
character repertoire.)
Replacement Character.
A character used as a substitute for an uninterpretable character from another encoding. The Unicode
Standard uses U+FFFD
replacement character for this function.
Replacement Glyph. A glyph used to render a character that cannot be
rendered with the correct appearance in a particular font. It often
is shown as an open or black rectangle. Also known as a missing
glyph. (See
Section 5.3, Unknown and Missing Characters.)
Reorderable Pair. Two adjacent characters A and B in a coded character sequence
<A, B> are a Reorderable Pair if and only if ccc(A) > ccc(B) > 0. (Used in the definition of Unicode Normalization Forms.) (See
definition D108 in
Section 3.11, Normalization Forms.)
Reserved Code Point.
Any code point of the Unicode Standard that is reserved for future assignment. Also known as an unassigned code point. (See definition D15 in
Section 3.4,
Characters and Encoding, and
Section 2.4, Code Points and Characters.)
RGI. Acronym for Recommended for General Interchange. This is a term used in Unicode Technical Standard #51, "Unicode Emoji", to refer to a subset of a larger set of emoji (or emoji sequences) that is intended to be widely supported across multiple platforms. See use of RGI.
Rich Text. Also known as styled text. The result of adding
information to plain text. Examples of information that can be added
include font data, color, formatting information, phonetic
annotations, interlinear text, and so on. The Unicode Standard does
not address the representation of rich text. It is expected that
systems and applications will implement proprietary forms of rich
text. Some public forms of rich text are available (for example, ODA,
HTML, and SGML). When everything except primary content is removed
from rich text, only plain text should remain.
Row. A range of 256 contiguous Unicode code points, where the first
code point is an integer multiple of 256. Two code points are in the
same row if they share all but the last two hexadecimal digits. (See
plane.)
S
SAM. Acronym for Syriac abbreviation mark.
SBCS. Acronym for single-byte character set. Any
one-byte character
encoding. This term is generally used in contrast with DBCS and/or
MBCS.
Scalar Value. (See
Unicode scalar value.)
Script. A collection of letters and
other written signs used to represent textual
information in one or more writing systems. For example, Russian is
written with a subset of the Cyrillic script; Ukranian is written
with a different subset. The Japanese writing system uses several
scripts.
Scriptio Continua. A writing
style without spaces or punctuation.
SCSU. Acronym for Standard Compression
Scheme for Unicode. See
Unicode Technical
Standard #6, “A Standard Compression Scheme for Unicode.”
Semi-Stable Comparison. (See deterministic comparison.)
SGML. Standard Generalized Markup Language. A standard framework,
defined in ISO 8879, for defining particular text markup languages.
The SGML framework allows for mixing structural tags that describe
format with the plain text content of documents, so that fancy text
can be fully described in a plain text stream of data. (See also HTML, XML,
and rich text.)
Shaping Characters. Characters that assume different glyphic forms
depending on the context.
Shift-JIS. A shifted encoding of the Japanese character encoding
standard, JIS X 0208, widely deployed in PCs.
Signature. An optional code
sequence at the beginning of a stream of coded characters that
identifies the character encoding scheme used for the following
text. (See Unicode signature.)
Singleton Decomposition. A canonical decomposition mapping from a character to a different single character.
(Used in the definition of Unicode Normalization Forms.) (See
definition D110 in
Section 3.11, Normalization Forms.)
Sinogram. A technical term for a Chinese character. In the Unicode Standard, sinograms are systematically referred to instead as CJK ideographs or Han ideographs. (See ideograph.)
SJIS. Acronym for Shift-JIS.
Small Letter. Synonym for lowercase letter. (See case.)
Sorting. (See
collation.)
Spacing Mark. A
combining character that is not a
nonspacing mark. (See definition D55 in
Section 3.6, Combination.) (See nonspacing mark.)
Stable Comparison. (See deterministic comparison.)
Stable Sort. A sort in which two records with a field that compares as equal will retain their relative order if sorted according to that field. This is a property of the sorting algorithm, and not of the comparison mechanism. For example, a bubble sort is stable, whereas a Quicksort is not.
Standard Korean Syllable Block.
(See Korean syllable block.)
Standardized Variation Sequence. A variation sequence defined in the UCD data file StandardizedVariants.txt. A standardized variation sequence cannot have an ideographic character as its base, and it makes use of a variation selector in the range U+FE00..U+FE0F or U+180B..U+180D. Note that U+FE0E and U+FE0F are reserved for special functions when applied to emoji base characters. See Unicode Technical Standard #51, "Unicode Emoji." The term standardized variation sequence is sometimes abbreviated as "SVS".
Starter. Any code point (assigned or not) with combining class of zero (ccc=0).
(Used in the definition of Unicode Normalization Forms.) (See
definition D107 in
Section 3.11, Normalization Forms.)
Static Form. (See
decomposable character.)
Styled Text. (See rich text.)
Subtending Mark. A format character whose graphic form extends under
a sequence of following characters—for example, U+0600
arabic number sign.
Supplementary Character. A Unicode encoded character having a
supplementary code point.
Supplementary Code Point. A Unicode code point between U+10000 and
U+10FFFF.
Supplementary Planes. Planes 1 through 16, consisting of the
supplementary code points.
Surrogate Character. A misnomer. It would be an encoded character
having a surrogate code point, which is impossible. Do not use this
term.
Surrogate Code Point. A
Unicode code point in the range U+D800..U+DFFF. Reserved for use by UTF-16, where a pair of
surrogate code units (a high surrogate followed by a low surrogate)
“stand in” for a supplementary code point.
Surrogate Pair. A
representation for a single abstract character that consists of a
sequence of two 16-bit code units, where the first value of the pair
is a high-surrogate code unit, and the
second is a low-surrogate code unit.
(See definition D75 in
Section 3.8, Surrogates.)
Syllabary. A type of writing system
in which each symbol typically represents both a consonant and a
vowel, or in some instances more than one consonant and a vowel.
Syllable. (1) An element of a syllabary. (2) A basic unit of
articulation that corresponds to a pulmonary pulse.
Syllable Block. A sequence of
Korean characters that should be grouped into a single square cell
for display. (See
Section 3.12, Conjoining Jamo Behavior.)
Symmetric Swapping. The process of rendering a character with a
mirrored glyph when its resolved directionality is right-to-left in
a bidirectional context. (See mirrored property and
Unicode Standard
Annex #9, “Unicode Bidirectional Algorithm.”)
T
Tagging. The association of attributes of text with a point or range
of the primary text. The value of a particular tag is not generally
considered to be a part of the “content” of the text. A typical
example of tagging is to mark the language or the font for a portion
of text.
Tailorable. A characteristic of an algorithm for which a
higher-level protocol may specify different results than those
specified in the algorithm. A tailorable algorithm without actual
tailoring is also known as a default algorithm, and the results of
an algorithm without tailoring are known as the default results.
TES. Acronym for transfer encoding
syntax.
TEX. Computer language designed for use in typesetting—in
particular, for typesetting math and other technical material.
(According to Knuth, TEX rhymes with the word blecchhh.)
Text Element. A minimum unit of text in relation to a particular
text process, in the context of a given writing system. In general,
the mapping between text elements and code points is many-to-many.
(See
Chapter 2, General Structure.)
Titlecase. Uppercased initial letter followed by lowercase letters
in words. A casing convention often used in titles, headers, and
entries, as exemplified in this glossary.
Titlo Letter. A superscripted letter (written above) used in Old Church Slavonic text.
Tonal Sandhi. A phonological
process whereby the tone associated with one syllable in a tonal
language influences the realization of a tone associated with a
neighboring syllable.
Tone Mark. A
diacritic or
nonspacing mark that represents a phonemic
tone. Tone languages are common in Southeast Asia and Africa.
Because tones always accompany vowels (the syllabic nucleus), they
are most frequently written using functionally independent marks
attached to a vowel symbol. However, some writing systems such as
Thai place tone marks on consonant symbols; Chinese does not use
tone marks (except when it is written phonemically).
Tonemic. Refers to the underlying,
distinctive units of a tonal system in a language. Tones of a tonal
language are often referred to by numbers (“tone 1,” “tone 2,” and
so on), and each tone has an idealized, specific tone level or
contour that is considered to be its tonemic value. The term was
created by analogy with phonemic.
Tonetic. Refers to the surface,
actual pitch realization of tones in a tonal system. Tonetic values
are what can be directly measured by tracking pitch contours in
actual speech recordings. The term was created by analogy with
phonetic.
Tonos. The basic accent in modern Greek, having the form of an acute
accent.
Trailing Consonant. (1)
In Korean, a jamo character with the Hangul_Syllable_Type property
value Trailing_Jamo (in the range U+11A8..U+11F9). Abbreviated as
T. (See definition D128 in
Section 3.12, Conjoining Jamo Behavior.) (2) Any final consonant in a syllable.
Trailing Surrogate. Synonym for
low-surrogate code unit.
Transcoding. Conversion of character data between different
character sets.
Transfer Encoding Syntax.
A reversible transformation applied to text and other data to allow
it to be transmitted—for example, Base64, uuencode.
Transformation Format. A mapping from a coded character sequence to
a unique sequence of code units (typically bytes).
Triangulation. (See
pivot conversion.)
Typographic Interaction.
Graphical application of one nonspacing mark in a position relative
to a grapheme base that is already occupied by another nonspacing
mark, so that some rendering adjustment must be done (such as
default stacking or side-by-side placement) to avoid illegible
overprinting or crashing of glyphs. (See definition D106 in
Section 3.11, Normalization Forms.)
U
UAX. Acronym for Unicode Standard Annex.
UCA. Acronym for Unicode Collation Algorithm.
UCD. Acronym for Unicode Character Database. (See
Section 4.1, Unicode Character Database.)
UCS. Acronym for Universal Character
Set, which is specified by International Standard ISO/IEC 10646,
which is equivalent in repertoire to the Unicode Standard.
UCS-2. ISO/IEC 10646 encoding form:
Universal Character Set coded in 2 octets, limited to the Basic
Multilingual Plane. (See
Appendix C, Relationship to ISO/IEC 10646.)
UCS-4. ISO/IEC 10646 encoding form:
Universal Character Set coded in 4 octets. (See
Appendix C, Relationship to ISO/IEC 10646.)
Umlaut. Two horizontal dots over a letter, as in German Köpfe. The
umlaut is not distinguished from the diaeresis in the Unicode
character encoding. (See
diaeresis.)
Unassigned Character. A code point that is not assigned to an abstract character. This refers to surrogate code points, noncharacters,
and reserved code points. (See
Section 2.4, Code Points and Characters.)
Unassigned Code Point.
Synonym for
reserved code point.
Undesignated Code Point. Synonym for
reserved code point.
Unicameral. A script that has no
case distinctions. Most often used
in the context of European alphabets.
Unicode. (1) The standard for digital representation of the characters used in writing all of the world's languages. Unicode provides a uniform means for storing, searching, and interchanging text in any language. It is used by all modern computers and is the foundation for processing text on the Internet. Unicode is developed and maintained by the Unicode Consortium:
http://www.unicode.org. (2) A label applied to software internationalization and localization standards developed and maintained by the Unicode Consortium.
Unicode Algorithm. The
logical description of a process used to achieve a specified result
involving Unicode characters. (See definition D17 in
Section 3.4,
Characters and Encoding.)
Unicode Character
Database. A collection of files providing
normative and informative Unicode character properties and mappings.
(See
Chapter
4, Character Properties, and the
Unicode Character Database.)
Unicode Collation Algorithm.
Tailorable text comparison mechanism used for searching, sorting,
and matching Unicode strings. See
Unicode Technical
Standard #10, “Unicode Collation Algorithm.”
Unicode Common
Locale Data Repository.
The repository of locale data in XML format maintained by the
Unicode Consortium (http://www.unicode.org/cldr/).
This repository provides information needed in the localization of
software products into a wide variety of languages, supplying (among
other things): date, time, number, and currency formats; sorting,
searching, and matching information; and translated names for
languages, territories, scripts, currencies, and time zones. (See
also Unicode Locale
Data Markup Language.)
Unicode Consortium. A standards development organization creating widely-used specifications related to character encoding, as well as for software internationalization and localization. Major projects are the Unicode Standard and the Unicode Locales Project, which defines repositories of standardized data needed
to develop software for particular regions and cultures. The Consortium was founded in 1991, and is headquartered in Mountain View, California. Its current members include major software corporations, governments, and academic institutions. See
http://www.unicode.org.
Unicode Encoding Form.
A character encoding form that assigns each Unicode scalar value to
a unique code unit sequence. The Unicode Standard defines three
Unicode encoding forms: UTF-8, UTF-16, and UTF-32. (See definition
D79 in
Section 3.9, Unicode Encoding Forms.)
Unicode Encoding Scheme. A specified byte serialization for a
Unicode encoding form, including the specification of the handling
of a byte order mark (BOM), if allowed. (See definition D94
in
Section 3.10, Unicode Encoding Schemes.)
Unicode Locale
Data Markup Language.
The XML specification for the exchange of locale data, defined by
Unicode Technical Standard #35,
"Unicode Locale Data Markup Language (LDML)." (See also Unicode Common
Locale Data Repository.)
Unicode Scalar Value. Any Unicode
code point except high-surrogate
and low-surrogate code points. In other words, the ranges of
integers 0 to D7FF16 and E00016 to 10FFFF16
inclusive. (See definition D76 in
Section 3.9, Unicode Encoding Forms.)
Unicode Signature. An implicit marker to identify a file as
containing Unicode text in a particular encoding form. An initial
byte order mark (BOM) may be used as a Unicode signature.
Unicode Standard Annex.
An integral part of the Unicode Standard published as a separate
document.
Unicode String. A code unit
sequence containing code units of a particular Unicode encoding form
(whether well-formed or not). (See definition D80 in
Section 3.9, Unicode Encoding Forms.)
Unicode Technical Note.
Informative publication containing information of possible interest
concerning the Unicode Standard or related topics.
Unicode Technical Report.
Formally approved Unicode Consortium publication containing
informative technical analysis of a topic related to the Unicode
Standard.
Unicode Technical
Standard. Formally approved specification published by the
Unicode Consortium that is related to, but not part of, the Unicode
Standard.
Unicode Transformation Format. An ambiguous synonym for either
Unicode encoding form or
Unicode encoding scheme. The latter terms
are now preferred.
Unification. The process of identifying characters that are in
common among writing systems.
UPA. Acronym for Uralic Phonetic Alphabet.
Uppercase. (See
case.)
URO. Acronym for Unified Repertoire and Ordering, the original set
of CJK unified ideographs used in the Unicode Standard.
User-Defined Character.
(See EUDC.)
User-Perceived Character.
What everyone thinks of as a character in their script.
UTF. Acronym for Unicode (or UCS)
Transformation Format.
UTF-2. Obsolete name for
UTF-8.
UTF-7. Unicode (or UCS) Transformation Format, 7-bit encoding form,
specified by RFC-2152.
UTF-8. A multibyte encoding for text that represents each Unicode character with 1 to 4 bytes, and which is backward-compatible with ASCII. UTF-8 is
the predominant form of
Unicode in web pages. More technically: (1)
The
UTF-8 encoding form. (2) The
UTF-8 encoding scheme. (3) “UCS Transformation Format 8,” defined in Annex D of ISO/IEC 10646:2003, technically equivalent to the definitions in the Unicode Standard.
UTF-8 Encoding Form. The
Unicode encoding form that assigns each Unicode scalar value to an
unsigned byte sequence of one to four bytes in length, as specified
in Table 3-6, "UTF-8 Bit Distribution." (See definition D92 in
Section 3.9, Unicode Encoding Forms.)
UTF-8 Encoding Scheme.
The Unicode encoding scheme that serializes a UTF-8 code unit
sequence in exactly the same order as the code unit sequence itself.
(See definition D95 in
Section 3.10, Unicode Encoding Schemes.)
UTF-16. A multibyte encoding for text that
represents each Unicode character with 2 or 4 bytes; it is not
backward-compatible with ASCII. It is the internal form of
Unicode in
many programming languages, such as Java, C#, and JavaScript, and in
many operating systems. More technically: (1)
The UTF-16 encoding
form. (2) The
UTF-16 encoding scheme. (3) “Transformation format for
16 planes of Group 00,” defined in Annex C of ISO/IEC 10646:2003;
technically equivalent to the definitions in the Unicode Standard.
UTF-16 Encoding Form.
The Unicode encoding form that assigns each Unicode scalar value in
the ranges U+0000..U+D7FF and U+E000..U+FFFF to a single unsigned
16-bit code unit with the same numeric value as the Unicode scalar
value, and that assigns each Unicode scalar value in the range
U+10000..U+10FFFF to a surrogate pair, according to Table 3-5,
“UTF-16 Bit Distribution.” (See definition D91 in
Section 3.9, Unicode Encoding Forms.)
UTF-16 Encoding Scheme.
The UTF-16 encoding scheme that serializes a UTF-16 code unit
sequence as a byte sequence in either big-endian or little-endian
formats. (See definition D98 in
Section 3.10, Unicode Encoding Schemes.)
UTF-16BE. The Unicode encoding
scheme that serializes a UTF-16 code unit sequence as a byte
sequence in big-endian format. (See definition D96 in
Section 3.10, Unicode Encoding Schemes.)
UTF-16LE. The Unicode encoding
scheme that serializes a UTF-16 code unit sequence as a byte
sequence in little-endian format. (See definition D97 in
Section 3.10, Unicode Encoding Schemes.)
UTF-32. A multibyte encoding for text that
represents each
Unicode character with 4 bytes; it is not
backward-compatible with ASCII. More technically: (1) The
UTF-32 encoding form. (2) The
UTF-32 encoding scheme.
UTF-32 Encoding Form. The
Unicode encoding form that assigns each Unicode scalar value to a
single unsigned 32-bit code unit with the same numeric value as the
Unicode scalar value. (See definition D90 in
Section 3.9, Unicode Encoding Forms.)
UTF-32 Encoding Scheme.
The Unicode encoding scheme that serializes a UTF-32 code unit
sequence as a byte sequence in either big-endian or little-endian
formats. (See definition D101 in
Section 3.10, Unicode Encoding Schemes.)
UTF-32BE. The Unicode encoding scheme
that serializes a UTF-32 code unit sequence as a byte sequence in
big-endian format. (See definition D99 in
Section 3.10, Unicode Encoding Schemes.)
UTF-32LE. The Unicode encoding scheme
that serializes a UTF-32 code unit sequence as a byte sequence in
little-endian format. (See definition D100 in
Section 3.10, Unicode Encoding Schemes.)
UTN. Acronym for Unicode Technical Note.
UTR. Acronym for Unicode Technical
Report.
UTS. Acronym for Unicode Technical
Standard.
V
Varia. Greek term for grave accent,
used in polytonic Greek character names.
Variation Selector. Any of three ranges of Unicode characters designated for use in defining a variation sequence. Variation selectors in the range U+FE00..U+FE0F are known as general-use variation selectors and are used for standardized variation sequences. Two of these, U+FE0E and U+FE0F, have specialized functions when used with emoji base characters. Variation selectors in the range U+180B..U+180D are known as Mongolian free variation selectors; their use is limited to standardized variation sequences for the Mongolian script. Variation selectors in the range U+E0100..U+E01EF are known as ideographic variation selectors and are used for ideographic variation sequences. Variation selectors are all nonspacing combing marks (General_Category=Mn). They have no graphic shape of their own; instead they function to pick out a particular, defined subset of potential graphic presentations for the base character to which they are applied. All variation selectors are default ignorable code points (DICP=Yes), meaning that if they are not interpretable in combination with their base character, they should be ignored for display, rather than shown with a nondisplayable glyph box, for example. See Section 23.4, Variation Selectors. The term variation selector is sometimes abbreviated as "VS".
Variation Sequence. A sequence consisting of precisely two code points: a base character (or a spacing mark [gc=Mc]) followed by a single variation selector. The two-character sequence is referred to as a variant of the base character or spacing mark. The function of the variation sequence is to pick out a particular, defined subset of potential graphic presentations of the base character (or spacing mark). Not all potential combinations of base characters and variation selectors have interpretations. Only the following variation sequences have valid interpretations: a standardized variation sequence, a registered ideographic variation sequence, and a variation sequence with an emoji base character defined in the data files associated with Unicode Technical Standard #51, "Unicode Emoji".
Virama. From Sanskrit. The name of a sign used in many Indic
and other Brahmi-derived scripts to suppress the inherent vowel of
the consonant to which it is applied, thereby generating a dead
consonant. (See
Section 12.1, Devanagari.) The sign varies in shape
from script to script, and may be known by other names in various
languages. For example, in Hindi it is known as hal or
halant, in
Bangla it is called hasant, and in Tamil it is called pulli.
Visual Ambiguity. A situation arising from two characters (or
sequences of characters) being rendered indistinguishably.
Visual Order. Characters ordered as they are presented for reading.
(Contrast with
logical order.)
Vocalization. Marks placed above, below, or within consonants to
indicate vowels or other aspects of pronunciation. A feature of
Middle Eastern scripts.
Vowel. In Korean, a jamo character with
the Hangul_Syllable_Type property value Vowel_Jamo (in the range
U+1161..U+11A2 or U+1160
hangul jungseong filler). Abbreviated as V.
(See definition D125 in
Section 3.12, Conjoining Jamo Behavior.)
Vowel Mark. In many scripts, a mark used to indicate a vowel or
vowel quality.
Vrachy. Greek term for breve accent, used in polytonic Greek character names.
W
W3C. Acronym for World Wide Web Consortium.
wchar_t. The ANSI C defined wide character type, usually implemented
as either 16 or 32 bits. ANSI specifies that wchar_t be an integral
type and that the C language source character set be mappable by
simple extension (zero- or sign-extension).
Well-Formed Code Unit Sequence. A code unit sequence that
follows the specification of a Unicode encoding form. (See
definition D85 in
Section 3.9, Unicode Encoding Forms.)
Writing Direction. The direction or orientation of writing
characters within lines of text in a writing system. Three
directions are common in modern writing systems: left to right,
right to left, and top to bottom.
Writing System. A set of rules for using one or more scripts to
write a particular language. Examples include the American English
writing system, the British English writing system, the French
writing system, and the Japanese writing system.
X-Y
XML. eXtensible Markup Language. A subset of SGML constituting a
particular text markup language for interchange of structured data.
The Unicode Standard is the reference character set for XML content.
(See also
SGML and rich text.) XML is a trademark of the World Wide
Web Consortium.
Ypogegrammeni. Greek term for subscript iota, used in polytonic Greek character names.
Y-variant. Two CJK unified ideographs with identical semantics and
non-unifiable shapes, for example, U+732B and U+8C93. (See
Z-variant.)
Z
Z-variant. Two CJK unified ideographs with identical semantics and
unifiable shapes, for example, U+8AAA and U+8AAC. (See
Y-variant.)
Zenkaku. (See
fullwidth.)
Zero Width. Characteristic of some spaces or format control
characters that do not advance text along the horizontal baseline.
(See
nonspacing mark.)