The names Θ, θ, ϑ may refer to any of several distinct quantities or operations.

For the Jacobi Theta functions, see JacobiTheta1.

For the theta graph, see GraphTheory[ThetaGraph].

For the Riemann theta function, see RiemannTheta.

For the risk measure Theta under the Black-Scholes model, see Finance[BlackScholesTheta].

$\mathrm{JacobiTheta1}\left(2.0\,0.5\right)$

$1.632025903$

$\mathrm{with}\left(\mathrm{GraphTheory}\right)\:$

$\mathrm{DrawGraph}\left(\mathrm{SpecialGraphs}:-\mathrm{ThetaGraph}\left(3\,4\,3\right)\right)$