Τ
Symbol  Format  Data 

Τ  Code Point 
U+03A4 
TeX 
\Tau 

SVG 
The capital Greek letter (capital tau) is visually very similar to the Latin capital letter T. For that reason, refer to the usage of Capital T for how the symbol appears in math.
The Greek letter τ (tau) is used in trigonometry as a constant to represent a full rotation around a circle in radians. The value of τ is approximately 6.28 and can be calculated by dividing any circle's circumference by its radius.