The colon alphabetic letter ꞉ is used in a number of languages and phonetic transcription systems, for vowel length in Americanist Phonetic Notation, for the vowels ⟨a꞉⟩ [ɛ] and ⟨o꞉⟩ [ɔ] in a number of languages of Papua New Guinea, and for grammatical tone in several languages of Africa. It resembles but differs from the colon punctuation mark, :. In some fonts, the two dots are placed a bit closer together than those of the punctuation colon so that the two characters are visually distinct. In Unicode it has been assigned the code U+A789 ꞉ MODIFIER LETTER COLON, which behaves like a letter rather than a punctuation mark in electronic texts. In practice, however, an ASCII colon is frequently used for the letter (U+003A : COLON).
In Windows and macOS, the letter colon can be used to emulate the punctuation colon in file names, where the punctuation colon is a reserved character that cannot be used.