# Theta function (disambiguation)

Theta functions $\vartheta(z;\tau)$ are special functions of several complex variables. Theta function may also refer to:
• Q-theta function $\theta(z;q)$, a type of q-series
• Theta function of a lattice $\Theta_\Lambda(\tau)$, a holomorphic function on the upper half-plane
• Mock theta functions $\mu(q), f(q), \phi(q), \psi(q), \chi(q)$, etc., a mock modular form of weight 1/2
• Ramanujan theta function $f(a,b)$