Solution
= Solution
An <eigenvalue> and <eigenvector> pair $(\lambda,v)$ for a square <matrix> $A$ satisfies
$$
\boxed{Av=\lambda v,\qquad v\ne0.}
$$
The <scalar> $\lambda$ and the coordinates of $v$ belong to the chosen <field>, usually $\mathbb R$ or $\mathbb C$. The nonzero condition is essential: the zero <vector> satisfies the equation for every $\lambda$ and therefore cannot define an <eigenvalue>.