Tau (upper case Τ, lower case τ) is the 19th letter of the Greek alphabet. In the system of Greek numerals it has a value of 300.
The lower-case letter τ is used as a symbol for:
- Tau in astronomy is a measure of opacity, or how much sunlight cannot penetrate the atmosphere
- Tau is the name of an island near Kilinailau , Greenwich Island , and Ocean Island.
- In Games Workshop's Warhammer 40,000 science fiction gaming universe, the Tau are an alien race.
- Tau is a symbol used from antiquity and is represented by a type of cross. There are those who accuse Christ of being the pirate of this ancient symbol, but it did not become a symbol of Christianity until a later date. As with Christianity, other ancient societies who used the "Tau" symbol also evolved its use to represent resurrection, reincarnation and blood sacrifice.
Tau is the name of a small village near Stavanger in Rogaland, Norway. You travel through Tau to get to the famous Pulpit Rock.