一、名词性从句

1.当从句的结构与意义都完整，说话人语气坚定用that，有疑问用whether/if。

2.当从句的结构完整，意义不完整，缺状语用where,when,why,how, 缺定语用whose或which。

3.当从句的结构不完整，缺主宾表，说事用what，说人用who, whom。

二、形容词性从句(定语从句)

1.当从句的结构不完整，缺主宾表，说事用that /which，说人用that/who/whom.

2.当从句的结构完整，意义不完整，缺状语用where(in/on+which),when(in/on/at/during+which),why(for+which).

3.当从句的结构不完整，缺定语用whose(=of which/whom +the+n. = the+n.+of which/whom)

三、副容词性从句(状语从句)

时间状语 when, whenever, while, as, before, after, until, till, by the time, as soon as, hardly…when, no sooner…than, the moment, the second, the minute, immediately, directly, instantly

地点状语 where, wherever

原因状语 because, as, since, now that

条件状语 if, unless, once, in case, as long as, on condition that

目的状语 so that, in order that, for fear that

结果状语 so…that, such…that

比较状语 than, as…as, not so/as…as, the more…the more

方式状语 as if, as though, as

让步状语 though, although, even if, even though, as, no matter what, whatever, no matter who, whoever, no matter which, whichever, no matter how, however, no matter when, whenever