An eigenbasis for a linear transformation is a basis
of
consisting entirely of eigenvectors
of
. Equivalently, a square
matrix has an eigenbasis iff it is diagonalizable.
If the columns of a matrix
are the vectors in an eigenbasis and the corresponding eigenvalues form the diagonal
matrix
,
then
A real symmetric matrix has an orthonormal eigenbasis, and a complex normal matrix also has an orthonormal eigenbasis.