Uh, guys, my book says: "Call $x\in\operatorname {End}V$ ($V$ fin. dim. vector space) semisimple if the roots of its minimal polynomial over $F$ are all distinct. Equivalently, ($F$ being algebraically closed), $x$ is semisimple if and only if $x$ is diagonalisable."
I'm confused; there exist diagonalisable matrices with repeated eigenvalues? (e.g., identity matrix)