宾语从句分为下面三点：
陈述句 用连接词that引导，可省略。
I think (that) you are right.
2. 一般疑问句，用if/whether连接。
I want to know if/whether he is right.
I want to know whether he is right or not. (这里不能用if)
3.特殊疑问句 用wh-词引导，根据需要选用。
I don't know who he is.
I want to know when he will leave.
定语从句是用来修饰名词的，放在名词的后面。引导定语从句的关系代词有：who, whom, whose, 分别在从句中作主语、宾语、定语，指人；that作主语、宾语，指人和物；which作主语、宾语，指物。
关系副词有：when,作时间状语，where，作地点状语，why，作原因状语。
I know the boy who is standing there.
I know the boy whom you are speaking with.
I know the boy whose father is a teacher.
I know the boy that is standing there.
I know the time when you were here last year.
I know the place where you are working.
I know the reason why you were late yesterday.
I like the house whose windows face the south.
后置定语就是放在名词后面的修饰词。
the room nearby
the book here
the ball there
其实学习英语只要把一些常用的词语、句型记住就可以了。
亲，祝你学习进步！