Advanced Linear Algebra
《Advanced Linear Algebra》 · 第 186 页 · Chapter 8「Eigenvalues and Eigenvectors」，Definition 条目 3)
The set of all eigenvectors associated with a given eigenvalue $\lambda$, together with the zero vector, forms a subspace of $V$, called the eigenspace of $\lambda$ and denoted by $E_\lambda$. This applies to both linear operators and matrices.