① 原因：because, since, now that(既然)as, for, this reason ...

② 结果：so that, so, therefore, consequently, so as to, as a result ...

③ 时间：after, before, when, while, as, until, as soon as, since, by the time, once, lately, presently, shortly after, currently, at present, nowadays ...

④ 条件：if, only if, once, unless, in the event (that), in case (that), provided that, on the condition that ...

⑤ 让步：though, although, even though (if), no matter what / how / when→ whatever / however / whenever ...

⑥ 目的：in order that, in order to, to,

⑦ 比较：than, as ... as, by comparison(相比较)，by contrast(相对照)...

新概念英语第三册课文