"Metro" 是指 "underground railway system"，即地铁系统。它的来源是法语 "métropoptain"，最初指巴黎的地铁系统，后来被用于全世界其他城市的地铁系统。
一些例句：
I take the metro to work every day. (我每天坐地铁上班。)
The metro system in Paris is one of the largest in the world. (巴黎的地铁系统是世界上最大的之一。)
Can you tell me how to get to the museum by metro? (你能告诉我如何坐地铁去博物馆吗？)