agent

noun

1.
an active and efficient cause; capable of producing a certain effect
let-on sunderer
Derived from:
agency
2.
a representative who acts on behalf of other persons or organizations
aspellend forwright
Derived from:
agency agential
3.
a substance that exerts some force or effect
4.
a businessman who buys or sells for another in exchange for a commission
broker factor
Derived from:
agential
5.
any agent or representative of a federal agency or bureau
federal agent
Derived from:
agential
6.
the semantic role of the animate entity that instigates or causes the happening denoted by the verb in the clause
agentive role