英语中定语从句里that能在定语从句里不充当成分吗?那时可以省略吗?还有在宾语从句里作成分吗?可以省略吗?什么情况可以的话把例句写出来

当that在句子里做定语从句的宾语就可省略，做主语不可省略。可以在宾语从句里作成分，也可以作名词从句的引导词。
e.g.1.I know the boy (that) I chatted with.
2.当宾语从句前有间接宾语时，that不可省。例如：
I told him that I had seen this movie.
我告诉他我已经看过这部电影。
3.如果当宾语从句前有插入语时，that不可省。例如：
We hope, as you know, that he will go abroad with us.
你也知道，我们希望他和我们到国外去。

在从句中充当宾语时可以省略：
I lost the book (that) my father bought.
定语从句中，that不能不充当成分，你说的是宾语从句吧！：
I don't know that you are a student. 在这里可以省略。that在宾语从句中也只做连接词，不做任何解释，不充当任何主要成分。
希望能对你有些帮助。

先说宾语从句吧.由陈述句转化来的宾从由that引导,这个你清楚吧,这些时候that没有意义,只是引导作用.e.g.,Tom said (that) he was not at home.口语和非正式情况下基本就省了.定从.that在定从中可以指人和物,在定从中...

定语从句中的引导词that在从句中作主语或宾语，作主语时不能省略，作宾语时一般可以省略。例如：
Do you know the man that is talking with your father.(作主语不能省略)
Do you know the man (that) your father is talking with.
宾语从句中的引导词that在从句中不充当句子成分，只起引导作用，一般情况下可以省略。例如：
He told me (that) he had lost his pen.
that不可省略的宾语从句:
1、当宾语从句前有插入语时，that不可省。例如：
We hope, as you know, that he will go abroad with us. 你也知道，我们希望他和我们到国外去。
2、当宾语从句前有间接宾语时，that不可省。例如：
I told him that I had seen this movie. 我告诉他我已经看过这部电影。
3、在两个并列的that宾语从句中，前面的这个that可以省略，后面的这个that不可以省略。例如：
He said (that) the book was very interesting and that(不省略) all the children like to read it.他说那本书很有趣，所有小孩都喜欢读。
4、在“it(形式宾语)+补语”之后作真正宾语的that宾语从句中，that不可省。例如：
I found it necessary that we should build a bridge here. 我发现我们有必要在这里建一座桥。
5、用that从句单独回答问题时，that不可省。例如：
—What did he hear? 他听说了什么事？
—That Kate had passed the exam. (他听说)凯特考试及格了。