Whitehead's lemma (Lie algebra)
In homological algebra, Whitehead's lemmas (named after J. H. C. Whitehead) represent a series of statements regarding representation theory of finite-dimensional, semisimple Lie algebras in characteristic zero. Historically, they are regarded as leading to the discovery of Lie algebra cohomology.
Source: Wikipedia — Whitehead's lemma (Lie algebra) (CC BY-SA 4.0)