An object is a noun that receives the action of the verb. A subject is the doer of the verb. And, a predicate completes the sentence; though this, too, can be a noun, a predicate noun completes the sentence, not the action. A noun that completes an action is the compliment. This does not mean, however, that other parts of speech cannot function as a compliment. A compliment can really be any word or words (phrase) that completes an action.