Tau

This article is about the letter of the Greek alphabet. For the mathematical constant, see Tau (mathematics). For other uses, see Tau (disambiguation).

Not to be confused with Tao, the Latin letters T or Ʈ, or the Cyrillic letters Т or Ꚍ.

Tau (/ˈtaʊ, ˈtɔː, ˈtɒ/ ^ⓘ; uppercase Τ, lowercase τ or τ; Greek: ταυ [taf]) is the nineteenth letter of the Greek alphabet, representing the voiceless dental or alveolar plosive IPA: [t]. In the system of Greek numerals, it has a value of 300.

The name in English is pronounced /taʊ/ or /tɔː/, and in Greek it is [taf]. This is because the pronunciation of the combination of Greek letters αυ can have the pronunciation of either [ai], [av] or [af], depending on what follows and if a diaeresis is present on the second vowel or an accent mark is present on the first vowel in Greek orthography.

Tau was derived from the Phoenician letter taw (𐤕). Letters that arose from tau include Latin T and Cyrillic Te (Т, т).