Advanced Linear Algebra
《Advanced Linear Algebra》 · 第 185-186 页 · Chapter 8「Eigenvalues and Eigenvectors」，Definition 条目 1)
Definition Let $V$ be a vector space over a field $F$ and let $\tau\in\mathcal L(V)$. 1) A scalar $\lambda\in F$ is an eigenvalue (or characteristic value) of $\tau$ if there exists a nonzero vector $v\in V$ for which $\tau v=\lambda v$.