Θθ

THETA

θῆτα · [tʰ]

The 8th letter of the Greek alphabet.

MATHEMATICS

  • Angle (θ) and polar coordinates.
  • Generic parameter in functions.

PROBABILITY

  • Unknown model parameter (θ).
  • Bayes: prior/posterior over θ.

STATISTICS

  • Model parameter to be estimated (θ).
  • MLE/MAP and inference for θ.

PRONUNCIATION

Ancient Greek
sound [tʰ]
Modern Greek
θήτα [ˈθita] · sound [θ]

IN FORMULAS

  • θ̂ = argmax L(θ)The maximum likelihood estimate of a parameter θ.
  • x = r cos θ, y = r sin θPolar coordinates: θ is the angle.

HOW TO WRITE IT — click to copy

lowercase
variant
uppercase

DON'T CONFUSE IT

  • ϑ θ δ ϕ ϑ is the cursive theta, open at the top right; θ is the closed oval with a bar.

Note: notations vary between books/fields; these are the most common usages.