To accept as satisfactory.

Approval implies that the thing approved has the endorsement of the approving agency-, however, the approval may still require confirmation by somebody else.

In management use, the important distinction is between approve and authorize.

Persons who approve something are willing to accept it as satisfactory for their purposes, but this decision is not final.

Approval may be by several persons.

The person who authorizes has final organization authority.

This authorization is final approval.

SOURCE: microsoft project