» This article is about the letter of the Greek alphabet. For other uses, see Tau (disambiguation). Tau (uppercase Τ, lowercase τ; []) is the 19th letter of the Greek alphabet. In the system of Greek numerals it has a value of 300. This letter in English is pronounced [taʊ], but in Modern Greek, this letter's name is pronounced [tuf]. This is because the pronunciation of the combination of Greek letters αυ has changed from ancient to modern times from one of /… (More on Tau)