agent 
英 [ˈeɪdʒənt]  美 [ˈeɪdʒənt] 
n. 代理人，代理商；间谍；动力；媒介；剂

例句：
He purchased it directly rather than through an agent. 

他是直接买的，没有通过代理商。

a written declaration by someone, authorizing another person to act as his agent 

某人授权另一人为代理人的书面声明

These young men regard themselves as the agents of change. 

这些男青年认为自己是变革的媒介。

Wind is an agent of pollination. 

风是授粉的媒介。

an enemy agent who had been assassinated 

被暗杀的一名敌方特工

All these years he's been an agent for the East. 

这些年来他一直是为东方国家效力的特工。