but, however, while (而)，only (只不过)等
表因果关系 for, so，therefore (因此)，then（那么）等
引导时间状语 after, before, when, while, as, until, till, since, as
从句
soon as等。
引导条件状语 if, unless等
难点链接
9） if(假如,如果)不能用whether. If you call him a fatty, he will get angry. 10） unless=if not You can not interview him unless you get the permission. 11）though/although都作为”虽然,尽管”可以互换,although用的更多一些. 后 面不可以有but但可以有yet/still.
He lied to me, I still believe him. 8) while表示的是”相反的”,也可以用but, however, on the other hand来代替. While some people have nothing to eat, others eat too much. 9) or连接句子或词组,表示 “或者”之意。 Which do you prefer, yellow, blue or red? Was he angry, or was he pretending? or, 也有“否则”的意思. 如：Be quick, or you will be late. 10) either … or/neither … nor和not only…but also并列主语时，谓语动词同样用就近原 则. Either Mary or her parents are going by bus. There is neither electricity nor free suppers in the hotel. Not only you but also I am from china. 11）so表示因此, 相当于therefore.（adv.） 如：They cost a lot of money, so use them carefully. It is very cold. Therefore, we should stay here. 12） then （adv）然后，而后，其次 如：I dropped in at her house and then I went home. 13）for引导的句子不可以放在句首，之前必须由逗号，表示推论的理由 They must be good friends, for they are always together. The day breaks, for the birds are singing.
