The Weyl character formula gives the formal character of a finite-dimensional irreducible Lie algebra representation of a complex
semisimple Lie algebra from its highest
weight. For a compact connected semisimple Lie group, it also gives the group
character of an irreducible group representation
restricted to a maximal torus. If is the highest weight,
is half the sum of the positive roots, and
is the Weyl
group, then
The denominator is the Weyl denominator, and the quotient expands as a finite sum whose coefficients are the weight multiplicities of the Lie algebra representation.