\thetaTheta (\theta) is a Greek letter commonly used in mathematics and science to represent angles, a variable, or a parameter. It is often used in trigonometry, calculus, and physics to denote an angle in polar coordinates or a phase angle in wave functions.
An angle of 45 degrees in radians.
\theta = \frac{\pi}{4}Theta as an angle in a trigonometric function.
\sin(\theta) = \frac{1}{2}Theta as a phase angle in a wave function, where \omega is the angular frequency and \theta_0 is the initial phase.
\theta(t) = \omega t + \theta_0