Noun

• S: (n) agent (an active and efficient cause; capable of producing a certain effect)
• S: (n) agent (a representative who acts on behalf of other persons or organizations)
• S: (n) agent (a substance that exerts some force or effect)
• S: (n) agent, factor, broker (a businessman who buys or sells for another in exchange for a commission)
• S: (n) agent, federal agent (any agent or representative of a federal agency or bureau)
• S: (n) agentive role, agent (the semantic role of the animate entity that instigates or causes the happening denoted by the verb in the clause)