When used as a diacritic mark, the term dot is usually reserved for the Interpunct ( · ), or to the glyphs 'combining dot above' ( ◌̇ ) and 'combining dot below' ( ◌̣ ) which may be combined with some letters of the extended Latin alphabets in use in Central European languages and Vietnamese.
Language scripts or transcription schemes that use the dot above a letter as a diacritical mark:
- In some forms of Arabic romanization, ġ stands for ghayin (غ); ḳ stands for qāf (ق).
- Traditional Irish typography, where the dot denotes lenition, and is called a ponc séimhithe or buailte "dot of lenition": ḃ ċ ḋ ḟ ġ ṁ ṗ ṡ ṫ. Alternatively, lenition may be represented by a following letter h, thus: bh ch dh fh gh mh ph sh th. In Old Irish orthography, the dot was used only for ḟ ṡ, while the following h was used for ch ph th; lenition of other letters was not indicated. Later the two systems spread to the entire set of lenitable consonants and competed with each other. Eventually the standard practice was to use the dot when writing in Gaelic script and the following h when writing in antiqua. Thus ċ and ch represent the same phonetic element in Modern Irish.
- Lithuanian: ė is pronounced as [eː], compared to ę, which is pronounced a lower [ɛː] (formerly nasalised), or e, pronounced [ɛ, ɛː].
- Maltese: ċ is used for a voiceless palato-alveolar affricate, ġ for a voiced palato-alveolar affricate, and ż for a voiced alveolar sibilant.
- Old English: In modernized orthography, ċ is used for a voiceless palato-alveolar affricate /t͡ʃ/, ġ for a palatal approximant /j/ (probably a voiced palatal fricative /ʝ/ in the earliest texts)
- Polish: ż is used for a voiced retroflex sibilant.
- The Sioux languages such as Lakota and Dakota sometimes use the dot above to indicate ejective stops.
- In Turkish, the dot above lowercase i and j (and uppercase İ) is not regarded as an independent diacritic but as an integral part of the letter. It is called a tittle.
- In the Rheinische Dokumenta phonetic writing system overdots denote a special pronunciation of r.
- Some countries use the overdot as a decimal mark.
In mathematics and physics, when using Newton's notation the dot denotes the time derivative as in . However, today this is more commonly written with a prime or using Leibniz's notation. In addition, the overdot is one way used to indicate an infinitely repeating set of numbers in decimal notation, as in , which is equal to the fraction 1⁄3, and , which is equal to 1⁄7.
- In IAST and National Library at Calcutta romanization, transcribing languages of India, a dot below a letter distinguishes the retroflex consonants ṭ, ḍ, ṛ, ḷ, ṇ, ṣ, while m with underdot (ṃ) signifies an anunaasika. Very frequently (in modern transliterations of Sanskrit) an underdot is used instead of the ring (diacritic) below the vocalic r and l.
- In romanizations of Afroasiatic languages, a dot below a consonant indicates emphatic consonants. For example, ṣ represents an emphatic s.
- In Asturian, ḷḷ (underdotted double ll) represents the voiced retroflex plosive, and ḥ (underdotted h) the voiceless glottal fricative.
- In academic notation of Old Latin, ẹ̄ (e with underdot and macron) represents the long vowel, probably /eː/, that developed from the early Old Latin diphthong ei. This vowel usually became ī in Classical Latin.
- In academic transcription of Vulgar Latin, used in describing the development of the Romance languages, ẹ and ọ represent the close-mid vowels /e/ and /o/, in contrast with the open-mid vowels /ɛ/ and /ɔ/, which were represented as e and o with ogonek (ę ǫ).
- In O'odham language, Ḍ (d with underdot) represents a voiced retroflex stop.
- Vietnamese: The nặng tone (low, glottal) is represented with a dot below the base vowel: ạ ặ ậ ẹ ệ ị ọ ộ ợ ụ ự ỵ.
- In Yoruba, the dot (or alternatively a small vertical line) is used below the o for an "open-o" sound, the e for an "open-e," and the s for an "sh" sound (ẹ, ọ, ṣ). The marking distinguishes these from the unmarked characters since the sound differences are meaningful.
- In Igbo, an underdot can be used on i, o, and u to make ị, ọ, and ụ. The underdot symbolizes a reduction in the vowel height.
- In Americanist phonetic notation, x with underdot x̣ represents a voiceless uvular fricative.
- Underdots are used in the Rheinische Dokumenta phonetic writing system to denote a voiced s and special pronunciations of r and a.
- In Marshallese, underdots on consonants represent velarization, such as the velarized bilabial nasal ṃ.
In Unicode, the dot is encoded at:
- U+0307 ȧ combining dot above (HTML
- U+0323 ạ combining dot below (HTML
There is also:
- U+02D9 a˙ dot above (HTML
- Turkish dotted and dotless I
- Arabic alphabet
- Mathematical operators and symbols in Unicode