A verb is related in various ways to the constituents in a sentence. The relations depend on the meaning of the particular verb. For example the NP the girl in the girl found a red brick is called agent or ‘doer’ of the action of finding. The NP a red brick is the patient or ‘recipient’ of the action. Part of the meaning of find is that its subject is as an agent and its logical object is a patient. That fact is reflected in the entry for find in the lexicon.
