Definition of "declaration"

A written or oral indication of a fact, opinion, intention, belief, etc.  examples

A list of items for various legal purposes, e.g. customs declaration.  examples

The act or process of declaring.  examples

(cricket) The act, by the captain of a batting side, of declaring an innings closed.  examples

(law) In common law, the formal document specifying plaintiff's cause of action, including the facts necessary to sustain a proper cause of action, and to advise the defendant of the grounds upon which he is being sued.  examples

(computing) The specification of an object, such as a variable or function, establishing its existence but not necessarily describing its contents.  examples