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Greek Language and Script

Q: Why are there two blocks of Greek characters in the Unicode Standard?

A: The layout of the Greek script in the Unicode Standard is an artifact of the history of Unicode and of ISO/IEC 10646. The Unicode Standard started out with just the Greek block (U+0370..U+03FF), with Greek characters laid out in compatibility with the modern Greek monotonic standard, ISO/IEC 8859-7, and with additions for some Coptic, ancient Greek, and Greek symbol letters. When the Unicode Standard had the repertoire from drafts of ISO/IEC 10646 merged in, as part of the standards compromise which resulted in the synchronization of the Unicode Standard and 10646, the Unicode Standard acquired a collection of pre-composed Greek characters which were intended for polytonic Greek usage. Those had to be placed somewhere, and a "compatibility" block was created at U+1F00..U+1FFF to accommodate them.

Q: Doesn't the existence of two blocks of Greek characters create problems for searching in Greek?

A: No. If you examine the code charts for the U+1F00..U+1FFF block of "extended" Greek carefully, you will note that all the polytonic Greek pre-composed characters have canonical mappings. This means that they are canonically equivalent to sequences consisting of the basic letters plus sequences of the basic letters plus combining voicing and accent marks. Any properly constructed Unicode search operation should treat canonical equivalents the same, so it should not matter whether one specifies a target match in terms of the pre-composed characters or in terms of the sequences of basic letters and combining marks. This situation for Greek is no different from the requirement for the Latin script that a search for a pre-composed Latin letter and the same letter with a combining accent mark produce the same results.

Q. Which block of Greek characters should I use?

A: The answer to that is that it depends what you are doing. But generally, the basic Greek block plus the use of the generic combining marks in the Combining Diacritical Marks block (U+0300..U+036F) is the best approach to polytonic Greek support. Some fonts do not directly support the display of the pre-composed extended Greek characters, and most current systems and browsers do a decent job for Greek using generic fonts. In any case, best display of Greek data—particularly polytonic Greek data—will result from use of specially-designed Greek fonts which handle all combinations of Greek accents optimally.

Q. What is the order of the accents on ancient Greek letters? Should they come before capital letters? If so, should they be spacing marks?

A: The order of accents on ancient Greek letters is the same as all other cases in Unicode: the accents are represented by combining marks that appear after the base letter. The canonical order can be seen either by looking at the polytonic Greek charts in the Unicode Standard or at the online normalization charts.

Q. Why does Unicode encode a separate character for the final sigma in Greek? Doesn't that violate the character-glyph model?

A: There are actually three reasons for this, all of which conspire to support the same result.

First, there is very extensive legacy practice for handling Greek characters. And in most of the major Greek character encodings, a character for the final sigma and a character for the non-final sigma are distinguished. This includes IBM Code Pages 423, 851, and 869, Windows Code Page 1253, the HP Greek8 code page, ISO 8859-7, and the Macintosh Greek code page. Ignoring this legacy and failing to encode a separate lowercase final sigma and non-final sigma would just have resulted in major interoperability issues for Unicode and all preexisting Greek data in those character encodings.

Second, the usability of a rendering model involving positional alternate glyphs for characters depends in part on the distribution and regularity of those forms in each particular script. The Arabic script is at one end of this continuum, since it is a cursive script, with predictable glyph shape variations for every character based on word position; such a script fits naturally into a processing model which has a basic character for each "letter", and then dynamically picks presentation forms (or even ligatures) based on positional analysis. Greek, on the other hand, is a non-cursive script, and in modern usage, at least, has basically just the single positional variant form, for sigma. In the latter case, burdening the rendering model with positional variant analysis is a bad engineering tradeoff, just to get the two sigmas to be represented by a single code. It is easier to simply equate the two sigma codes for operations which are concerned with word content, for example.

Finally, a detailed analysis of Greek corpora and the usage of final sigma and non-final sigma makes it clear that no simple positional context rule would cover all the cases. The rule is actually rather complex and has lots of exceptions, for abbreviations and other special cases. That the "rule", if indeed there is a single rule, is so complex, indicates that 1) it would be difficult to implement, and would probably lead to nagging inconsistencies between implementations, and 2) that the long history of final sigma and non-final sigma as character entities (encoded or not) has resulted in them starting to accrue some independent "characterhood", enabling people to think of uses for them outside their canonical positions.

Taken all together this was an easy call: Unicode should (and does) have a separate character code for the Greek final sigma and the non-final sigma.

Q: How do I represent a mute iota?

A: In Greek, the vowels α η ω can be followed by a mute iota. In those cases, the iota is written in smaller size, under the letter: ᾳ ῃ ῳ , and it is represented using U+0345 COMBINING GREEK YPOGEGRAMMENI.

In initial capitalization and in all-caps words, one can find a wide range of graphic presentations of the mute iota:

visual
appearance of mute iota

The proper sequence of characters to use depends on the graphic presentation you want to achieve:

  • for 1-3, use U+0345 COMBINING GREEK YPOGEGRAMMENI

  • for 4, use U+03B9 GREEK SMALL LETTER IOTA

  • for 5-7, use U+0399 GREEK CAPITAL LETTER IOTA (may be styled in small caps)

Conversely, rendering systems usually render a mute iota represented by U+0345 COMBINING GREEK YPOGEGRAMMENI as one of 1-3, render a mute iota represented by U+03B9 GREEK SMALL LETTER IOTA as 4 and render a mute iota represented by U+0399 GREEK CAPITAL LETTER IOTA as one of 5-7.

However, it is perfectly acceptable for a rendering system to produce any of the graphic presentations of mute iota from any of the coded character representations, much like it is perfectly acceptable for a rendering system to produce a small caps graphic display of lowercase text.

Note that this has implications for case conversion. In particular, U+0345 contains information that can be lost when converting to uppercase. This is not unusual with case mappings: converting "McGowan" or "vedereLa" to uppercase also loses information. [EM]

Q. Where can I find a detailed, scholarly analysis of all the problems related to the Greek script and Unicode?

A: Greek Unicode Issues has more than you will probably ever need to know about all the Greek encoding issues related to Unicode. It also has links to other sites dealing with Greek.