Combining diacritics

In digital typography, combining characters are characters that are intended to modify other characters. The most common combining characters in the Latin script are the combining diacritical marks (including combining accents).

Unicode also contains many precomposed characters, so that in many cases it is possible to use both combining diacritics and precomposed characters, at the user's or application's choice. This leads to a requirement to perform Unicode normalization before comparing two Unicode strings and to carefully design encoding converters to correctly map all of the valid ways to represent a character in Unicode to a legacy encoding to avoid data loss. In Unicode, the main block of combining diacritics for European languages and the International Phonetic Alphabet is U+0300–U+036F. Combining diacritical marks are also present in many other blocks of Unicode characters. In Unicode, diacritics are always added after the main character, so it is possible to add several diacritics to the same character, although as of 2010^[update], few applications support correct rendering of such combinations.

OpenType has the ccmp "feature tag" to define glyphs that are compositions or decompositions involving combining characters.

Codepoints U+032A and U+0346–034A are IPA symbols:

Codepoints U+034B–034E are IPA diacritics for disordered speech:

U+034F is the "combining grapheme joiner" (CGJ) and has no visible glyph.

Codepoints U+035C–0362 are double diacritics, diacritic signs placed across two letters.

Codepoints U+0363–036F are medieval superscript letter diacritics, letters written directly above other letters appearing in medieval Germanic manuscripts, but in some instances in use until as late as the 19th century. For example, U+0364 is an e written above the preceding letter, to be used for Early Modern High German umlaut notation, such as uͤ for Modern German ü.

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