Diacritic

A diacritic or diacritic(al) mark or diacritic(al) sign, in several writing systems, is a little sign added on a character, modifying slightly this character, in order to give any information about the pronunciation or, sometimes, in order to distinguish a word from another word. For instance: the character e becomes é, c becomes č, o becomes ø, s becomes ș, ω becomes ώ, и becomes й, nh becomes n·h.

Concerned writing systems

Diacritics may occur in most writing systems.

• Some diacritics are unique to one writing system. For instance, the diacritic called shadda, indicating that a consonant is geminate (doubled), is typical of the Arabic alphabet: ر (d) with a shadda becomes دّ (dd) .
• Several diacritics may be shared by different but resembling writing systems. It is notably the case for the Roman, the Greek and the Cyrillic alphabets, which can share the acute accent (´) and the dieresis (¨).

Modified letters

A letter with a diacritic is called a modified letter.

• In some languages, a modified letter (with a diacritic) is considered as a simple variant of the basic letter (without diacritic). For instance, in Portuguese, ç is nothing but a variant of the letter c.
• In other languages, a modified letter may be considered as an independent letter, having its own place in the alphabet and being totally distinct from the diacritic-less letter. For instance, in Turkish, ç is a different letter from c.

Quantity and frequency

The quantitity and the frequency of diacritics may differ.

• Some languages have no diacritics at all in the current use. It is notably the case of English and Malay (although some diacritics may be seen in foreign words, as in English café or cafe).

• A lot of languages use diacritics, which frequency varies a lot according to the language in question. For instance, diacritics are quite rare in Dutch, which uses only ë, and in Italian, which uses mainly à, è, é, ì, ò, ù. On the opposite, other languages use a lot of different diacritics, sometimes placed on nearly each sentence or on nearly each word, as in Vietnamese or in classical Greek.

Mandatory or optional uses

Diacritics may be mandatory or optional, depending on the language in question.

In the writing systems which distinguish uppercase and lowercase letters, a few languages tend to use diacritics in current writings where lowercases and uppercases are mixed, but supress certain diacritics in all-uppercase sequences. This is a rule in Greek; this also a frequent—but nonstandard—use in Spanish and French: Greek νερό (“water”) becomes ΝΕΡΟ, Spanish águila (“eagle”) becomes ÁGUILA or less correctly AGUILA, French côté (“side”) becomes CÔTÉ or or less correctly COTE.