肯定句：I waited until midnight. 否定句：I did not leave until midnight.
注意点：1)not until…在句首，主句用倒装 Not until you had explained how did I manage to do it.
2) It is not until…that…引导的强调句 It was not until it was dark that he came back.
3.Hardly/scarcely…when, no sooner…than, as soon as表示为“一```就```”
I had hardly/scarcely got home when it began to rain.
I had no sooner got home than it began to rain. It began to rain as soon as I got home.
条件状语从句分为两大类：真实条件句(主将从现)和虚拟条件句(虚拟语气)。引导条件状语从句的连词有：if, even if/though, unless/ if …not, as long as/ so long as, as far as/so far as, provided/providing (that), on condition that 等。条件状语从句中如果主句是将来时，条件状语从句用一般现在时。
1.unless 和if…not unless 相当于if…not
You will fail unless you study hard.
You will not fail if you study hard.
If she were not too silly,she would understand.
You may go there ,as long as you keep quite.
I will go provided that you go too.
I shall give you the book on condition that you return it tomorrow.
引导让步状语从句的连词有：though, although, even if/ though, however, no matter how, no matter what, no matter who等。
1.though, although不可与but连用，但可以和yet , still连用.
Though/Although it is raining ,they are still running outside.
2. “no matter+疑问词”或“疑问词+后缀ever”
No matter what happened, he would not mind.
Whatever happened, he would not mind.
3.even if/ though表示“即使”
He doesn’t want to marry her even if/ though he loves her very much.
引导原因状语从句的连词有：because, since, as , now that ,considering that, for the reason that , due to the fact that,owing to the fact that等。