Tau Symbol

Τ is the capital form of the Greek letter tau, visually identical to the Latin letter T. Owing to this resemblance it is seldom used as an independent mathematical symbol, while the lowercase τ is common for torque, shear stress, time constants, and the circle constant 2π. The capital form appears mainly where typographic consistency with other capital Greek letters is required.

The Greek small letter tau (τ) is the nineteenth letter of the Greek alphabet. In physics it commonly denotes torque, shear stress, and time constants, while in mathematics it serves as a general constant or parameter, naming the divisor-counting function in number theory and the torsion of a space curve in differential geometry. Some authors also propose τ as a symbol for the circle constant 2π.