happen过去式：happened；过去分词：happened；第三人称单数：happens；现在分词：happening。
happen英[ˈhæpən]，美[ˈhæpən]
v.(尤指偶然)发生，出现;(作为结果)出现，发生;碰巧;恰好
用法
happen是不及物动词。happen在中学英语教材中的用法主要有以下三种：
1."sth.+happen+地点/时间"，意为"某地/某时发生了某事"。例如：
An accident happened in that street.那条街发生了一起事故。
What's happening outside？外面发生什么事了？
2."sth.+happen to+sb."意为"某人出了某事(常指不好的事发生在某人身上)"。例如：
A car accident happened to him yesterday.昨天他发生了交通事故。
What happened to you？(=What was wrong/the matter with you？)你怎么啦？
3."sb.+happen+to do sth."意为"某人碰巧做某事"。例如：
I happened to meet her in the street.我碰巧在街上遇见她。
happen例句1、We cannot say for sure what will happen.
我们无法确定会发生什么事。
2、She wondered what would happen if her parents found her.
她不知道如果父母找到自己会有什么结果。
3、If we had been spotted at that point,I don't know what would have happened to us.
如果当时我们被发现了，我不知道会有什么后果。
