Introduction to Representation Theory
《Introduction to Representation Theory》 · 第 23 页 · Section 2.9「Lie algebras」，Definition 2.9.7
Definition 2.9.7. A representation of a Lie algebra $\mathfrak g$ is a vector space $V$ with a homomorphism of Lie algebras $\rho:\mathfrak g\to\operatorname{End}V$.