diacriticssignals

Diacritic signals, or diacritics, are marks added to letters to modify pronunciation or convey linguistic information within a writing system. They function as signals to readers about vowel quality, tone, stress, length, nasalization, or consonantal change, and they are integral to many orthographies.

Common diacritics include acute (´), grave (`), circumflex (^), and tilde (~) above the base letter, as in é, è, ê, and ñ. The diaeresis (¨) marks separate vowels, as in ä and ö; the cedilla (ç) alters c; caron or hacek (č, š, ž) signals postalveolar or palatalized sounds; macron (ā) and breve (ă) indicate length. Diacritics can signal stress (as in many Spanish and French words), vowel quality, tone in Vietnamese, or nasalization in Portuguese.

Encoding and processing. In Unicode, diacritics can be encoded as precomposed characters (é) or as a base letter with combining marks (e + ́). Normalization forms NFC and NFD govern how these representations are stored and compared. Diacritics affect sorting, search, and rendering, and diacritic-insensitive search is common in information retrieval. OCR, spell checking, and natural language processing must account for diacritics to avoid errors.

Typography and rendering. Typeface designers must provide glyphs for diacritics and ensure proper spacing, especially for languages that stack multiple marks. Some scripts require complex diacritic stacking, which can complicate typography and font design.

Usage. Diacritics are widespread across languages and scripts, preserving pronunciation, meaning, and etymology. Fidelity to diacritics is important in dictionaries, education, digital typography, and language technology.