happen過去式：happened；過去分詞：happened；第三人稱單數：happens；現在分詞：happening。
happen
英[?h?p?n]，美[?h?p?n]
v.(尤指偶然)發生，出現;(作為結果)出現，發生;碰巧;恰好
用法
happen是不及物動詞。happen在中學英語教材中的用法主要有以下三種：
1."sth.+happen+地點/時間"，意為"某地/某時發生了某事"。例如：
An accident happened in that street.那條街發生了壹起事故。
What's happening outside？外面發生什麽事了？
2."sth.+happen to+sb."意為"某人出了某事(常指不好的事發生在某人身上)"。例如：
A car accident happened to him yesterday.昨天他發生了交通事故。
What happened to you？(=What was wrong/the matter with you？)妳怎麽啦？
3."sb.+happen+to do sth."意為"某人碰巧做某事"。例如：
I happened to meet her in the street.我碰巧在街上遇見她。
happen例句1、We cannot say for sure what will happen.
我們無法確定會發生什麽事。
2、She wondered what would happen if her parents found her.
她不知道如果父母找到自己會有什麽結果。
3、If we had been spotted at that point,I don't know what would have happened to us.
如果當時我們被發現了，我不知道會有什麽後果。