在英语语法中,名词性从句和状语从句是两种重要的从句类型。名词性从句在句子中起名词作用,可以作为主语、宾语、表语或同位语,常由连词如"that", "whether"等引导。状语从句在句子中起状语作用,表示时间、原因、条件等,常由连词如"when", "if"等引导。掌握这两种从句的用法对于英语学习者来说非常必要。
名词性从句
名词性从句是指在句子中起到名词作用的从句。它可以作为主语、宾语、表语或同位语。名词性从句通常由连词 that, whether, if, who, whom, whose, what, when, where, why, how 引导。
例如:
- I know [that he is coming].(作宾语)
- [What you said] is true.(作主语)
- His question is [whether she will come].(作表语)
- The fact [that he passed the exam] surprised me.(作同位语)
名词性从句的引导词可以省略,而且常常被省略。需要注意的是,当名词性从句作为宾语时,如果它的主语与主句的主语相同,那么在名词性从句中可以省略主语,只保留谓语动词。
例如:
- I know [he is coming].(作宾语,省略了 that)
- She said [she would come].(作宾语,省略了 that)
状语从句
状语从句是指在句子中起到状语作用的从句。它可以表示时间、原因、条件、结果、让步、方式等。状语从句通常由连词 when, while, before, after, since, until, because, since, if, whether, though, although, even if, as, so that, in order that, as if, as though, as long as 等引导。
例如:
- [When I was young], I used to play with my friends.(表示时间)
- [If it rains], we will stay at home.(表示条件)
- [Although he is tired], he keeps working.(表示让步)
- [So that she can learn English well], she studies hard.(表示目的)
需要注意的是,状语从句通常放在主句之后,两者之间用逗号隔开。但是,如果状语从句是表示时间的 when, while, before, after, until 等连词引导的,通常放在主句之前。