before lunch/class/the match..... (prep) before running/swimming/taking a shower..... (prep) before he comes back/I left/we find the right answer. (conj). I have never seen him before .Did you go to the village before ? (adv.)
时间上:before 可用在时间状语从句中,例如:He has left the room before I came in. 位置上:in front of 在……前面,是指两个独立的物体,例如:The post office is in front of the shop. in the front of在……的前部,是指一个东西在另外一个东西的前...