Someone or something that takes part in some action; a doer, an agent.
The entity that performs a role (in use case analysis).
A person who acts a part in a theatrical play or (later) in film or television; a dramatic performer.
The subject performing the action of a verb.
A person who takes part in dialogue or conversation.
A man in the middle of the line in a minstrel show who questions the end men and acts as leader.
A decree of a court.
An interlocutory judgement or sentence.