Definition:Bounded Linear Operator/Inner Product Space

Definition
Let $H$ be a Hilbert space.

Let $A: H \to H$ be a linear operator.

$A$ is a bounded linear operator


 * $\exists c > 0: \forall h \in H: \left\Vert{A h}\right\Vert_H \le c \left\Vert{h}\right\Vert_H$

That is, a bounded linear operator is a bounded linear transformation from a Hilbert space to itself.