1.表示“某地(某時)發(fā)生了什么事”,常用“sth.+ happen +地點/時間”這一結(jié)構(gòu)來表達,此時主語應是事情.例如：
The story happened in 1998
.這個故事發(fā)生在1998年。
An accident happened in that street.
那條街上發(fā)生了一起事故。
2.表示“某人出了某事(常指不好的事)”,要用“sth.+ happen+to sb.”這一結(jié)構(gòu)來表達.例如：
A car accident happened to her this morning.
今天上午她發(fā)生了交通事故。
What happened to you?你怎么啦?
3.表示“某人碰巧做某事”,要用“sb.+ happen+ to do sth.”這一結(jié)構(gòu)來表達.例如：
I happened to meet a friend of mine in the street yesterday.
昨天我碰巧在街上遇到了我的一個朋友。
4.happen表示“碰巧或恰巧發(fā)生某事”時,還可用“It happens / happened that...”這一結(jié)構(gòu)來表達。例如：
It happened that Brian and Peter were at home that day.
碰巧那天布萊恩和彼得在家了。
It happened that he had to take part in a meeting that afternoon.
碰巧那天下午他不得不參加一個會議。
注：that從句中的主語是人時,此種結(jié)構(gòu)可以與“sb.+ happen + to do sth.”結(jié)構(gòu)互換。例如：
It happened that Brian and Peter were at home that day.
= Brian and Peter happened to be athome that day.
5.happen為短暫性動詞，不能與表示一段時間的狀語連用。