agent

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

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

Any agent or representative of a federal agency or bureau.

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

“their research uncovered new disease agents”

A representative who acts on behalf of other persons or organizations.

A substance that exerts some force or effect.