bounded operator
linear transformation L between normed vector spaces X and Y for which the ratio of the norm of L(v) to that of v is bounded by the same number, over all non-zero vectors v in X
normal operator
(on a complex Hilbert space) continuous linear operator
compact operator
type of continuous linear operator
unitary operator
surjective bounded operator on a Hilbert space preserving the inner product
subnormal operator
type of operator in operator theory in mathematics
contraction
bounded linear operator between normed spaces, whose operator norm is not greater than 1