高中英语中,since,before,when的区别

Since 自从,在某个时间后It was the first time they had won since 1974.
某事情由某时间开始,I have known her since 1983.
因为,既然 since they have obviously foegotten to phone me,I will have to phone them.
before 在某某前面,之前,You will call me any time before 10 o'clock.
They should be here before long.=soon
Turn the lights off before you leave.
when 当某某的时候,He jumped up when the phone rang.
指将来的事,when用现在时.I will call you when I am ready.
行将发生的事,既然,考虑到 Why do you want to more money when you have got enough already?
I will ask her when she comes.

完成时+since，自从…；before+后来发生的事（现在分词或名词），在…之前；when+进行时或一般现在时，在…的时候
例句：I have been waiting here since eight o'clock.
I finished my homework before going to sleep.
I was cleaning my room when my mother came in.