SynonymDefinitionAntonym.com - English Synonym Dictionary

The semantic role of the animate entity that instigates or causes the happening denoted by the verb in the clause

An active and efficient cause; capable of producing a certain effect

A businessman who buys or sells for another in exchange for a commission

A representative who acts on behalf of other persons or organizations

Any agent or representative of a federal agency or bureau

A substance that exerts some force or effect