Definition of gamma function in US English:

gamma function

noun

  • A function (symbol Γ) which extends the notion of factorial n (written n!) from positive whole numbers to real and complex variables, given by Γ(z) = ∫∞ 0 t z − 1 e −t dt.

Origin

Mid 19th century; earliest use found in Reports of the British Association for the Advancement of Science.