# Cyclic vector for a linear operator

Saying that " T is diognalizable. If T has n distinct eigenvalues and {a1,...,an} be a basis of eigenvectors of T" means that if B is the matrix having the vectors {a1,..., an} as columns then $B^{-1}TB= D$ where D is the diagonal matrix having the eigenvalues of T on its diagonal. Now, what is the definition of "cyclic vector"?