Tau
/taʊ/noun
The nineteenth letter of the Greek alphabet, also used as a symbol in mathematics, science, and theology.
Did you know?The Greek letter tau derives from the Phoenician letter taw, whose early form resembled a cross; in Christian symbolism, the Tau cross became associated with Saint Francis of Assisi and the Franciscans.
Etymological Timeline
Late 2nd millennium BCE
Proto-Canaanite
𐤕
“A marked sign, probably represented by a cross-like symbol”
1st millennium BCE
Phoenician
𐤕 taw
“The letter taw, meaning “mark” or “sign””
1st millennium BCE
Aramaic
ת tav
“A letter descended from the Phoenician taw”
8th–6th Century BCE
Ancient Greek
ταῦ tau
“The nineteenth letter of the Greek alphabet”
1st Century CE
Latin
tau
“The Greek letter name, adopted into Latin writing”
Modern English
English
tau
“The Greek letter τ, used for quantities such as torque, shear stress, and the circle constant 2π”