1.當從句的結構與意義都完整，說話人語氣堅定用that，有疑問用whether/if。

2.當從句的結構完整，意義不完整，缺狀語用where,when,why,how, 缺定語用whose或which。

3.當從句的結構不完整，缺主賓表，說事用what，說人用who, whom。

1.當從句的結構不完整，缺主賓表，說事用that /which，說人用that/who/whom.

2.當從句的結構完整，意義不完整，缺狀語用where(in/on which),when(in/on/at/during which),why(for which). 

3.當從句的結構不完整，缺定語用whose(=of which/whom the n. = the n. of which/whom)

時間狀語 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

地點狀語 where, wherever

原因狀語 because, as, since, now that

條件狀語 if, unless, once, in case, as long as, on condition that

目的狀語 so that, in order that, for fear that

結果狀語 so…that, such…that

比較狀語 than, as…as, not so/as…as, the more…the more

方式狀語 as if, as though, as

讓步狀語 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