diacritic

A diacritic is a glyph added to a letter to modify its pronunciation, stress, or meaning. In written language diacritics are called diacritical marks, and the letter with the mark is sometimes referred to as a diacritic letter. Diacritics occur in many alphabets and can appear above, below, through the base character, or as a separate combining mark.

Common diacritics include the acute accent (é), grave accent (è), circumflex (ê), tilde (ã, ñ), diaeresis or umlaut (ë, ï), cedilla (ç), caron or hacek (č), ogonek (ą), ring (å), macron (ā), breve (ă), and dot above or below (ż, ḍ). They serve various purposes: indicating pronunciation or vowel quality, signaling tone or stress, or distinguishing between otherwise identical forms. For example, Spanish uses accents to mark stressed syllables and to distinguish certain words; Vietnamese uses tone marks to convey pitch; French uses diacritics that reflect historical vowel changes.

In computing, diacritics may be represented as a single precomposed character or as a base letter plus one or more combining diacritical marks. Unicode supports both approaches, which affects text normalization, rendering, and processing. Some scripts rely heavily on diacritics for phonemic distinctions, while others use them mainly for loanwords or proper names. The positioning of diacritics (above, below, or through the letter) and whether they are spacing or nonspacing marks influence how text is stored and displayed.

Etymology-wise, the term diacritic comes from Greek dia- ‘through’ and kritikos ‘able to discern,’ via French diacritique. Diacritics play a central role in orthography by distinguishing meaning and guiding pronunciation, with usage varying across languages and standards.