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.

A letter with a diacritic is called a modified letter.

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 (¨).

Roman alphabet

 * accent
 * acute accent (´): á, ć, é, ǵ, í, ń, ó, ŕ, ś, ú, ẃ, ý, ź...
 * grave accent (`): à, è, ì, ò, ù, ẁ, ỳ...
 * double acute accent ( ˝ ): ő, ű...
 * circumflex accent ( ˆ ): â, ĉ, ê, ĝ, ĥ, î, ĵ, ô, ŝ, û, ŵ, ŷ, ẑ...
 * breve ( ˘ ): ă, ĕ, ğ, ĭ, ŏ, ŭ...
 * caron or haček ( ˇ ): č, ď (Ď), ě, ǧ, ň, ř, š, ť (Ť), ž...
 * dieresis or umlaut (¨): ä, ë, ï, ö, ü, ÿ...
 * macron ( ¯ ): ā, ē, ī, ō, ū, ȳ...
 * cedilla ( ¸ ): ç, ş...
 * comma : ģ (Ģ), ķ, ļ, ņ, ș, ț...
 * ogonek or nosinė ( ˛ ): ą, ę, į, ǫ, ų...
 * dot
 * overdot ( ̇ ): ċ, ė, ż...
 * underdot (  ̣ ): ạ, ḍ, ẹ, ḥ, ị, ọ, ṣ, ṭ, ụ, ẓ...
 * interpunct (·): ch·, g·, l·l, n·h, s·h...
 * hook or dấu hỏi ( ̉ ): ả, ɓ (Ɓ), ƈ, ɗ (Ɗ), ẻ, ƒ (Ƒ), ɠ (Ɠ), ỉ, ƙ (Ƙ), ɱ (Ɱ), ŋ (Ŋ), ỏ, ƥ (Ƥ), ƭ (Ƭ), ủ, ʋ, ⱳ, ỷ, ƴ, ȥ...
 * horn or dấu móc ( ̛ ): ơ, ư...
 * ring
 * ring above or kroužek ( ˚ ): å, ů...
 * ring below ( ˳ ): ḁ...
 * tilde ( ̃ ): ã, ẽ, ĩ, ñ, õ, ũ...
 * apostrophe (’): c’h...
 * single opening quotation mark (‘): g‘, o‘...
 * stroke (/): ð (Ð), đ (Đ), ħ (Ħ), ł, ø...

Greek alphabet

 * accent
 * acute accent (´)
 * grave accent (`)
 * perispomene, shaped like a circumflex accent ( ˆ ) or like a tilde ( ̃ )
 * dieresis (¨)
 * iota subscript (ͺ): ᾳ, ῃ, ῳ
 * rough breathing or dasia ( ῾  )
 * smooth breathing or psili ( ᾿  )

Status of 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 some borrowings, as in English café or cafe, a word of French origin).


 * 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.

Pedagogical use
Some languages use certain diacritics only as a pedagogical help and remove them in general use. For instance, Russian only uses the acute accent (´) in learner-oriented publications, in order to show the place of the stress.

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

Some users of French keep diacritics on all-uppercase sequences but remove them on initial uppercases when followed by lowercases, so école “school” becomes École or less correctly Ecole.

In Italian, the only frequent diacritics are an acute accent and sometimes a grave accent on the last letter of a word. This accent may be replaced by an apostrophe at the right of the last letter, especially in all-uppercase sequences, but this is nonstandard: libertà (“freedom”) becomes LIBERTÀ or less correctly LIBERTA’.

Number of affected characters
In general, a diacritic affects one character.

In a few languages, however, a diacritic is used to modify a group of letters, for instance in Breton (c’h), in Manx (çh), in Catalan (l·l), in Occitan (n·h, s·h) or in Francoprovençal (ch·).