“that”这个词在英语中很常见，有很多不同的用法。你注意到'that'在前面句子中的用法了吗?在这种情况下，'that'被用作关系代词作补语。通常，‘that’可以用在句子中，也可以完全省去。例如，许多学英语的学生知道，根据具体情况，可以省略'that '。这篇关于“that”用法的指南将帮助你理解什么时候该用这个词，什么时候可以不用它。
That在句子开头用作限定词，表示离说话人很远的一个宾语。注意that作为限定词的复数形式是those。'That'和'those'通常与'there'连用，表示宾语离说话人不近。
例如：
That's my friend Tom over there.
That's a pencil you have in your hand.
Those paintings are by Cezanne.
That is my house on the corner of the street.
'That'可以用作关系代词连接两个从句。在这种情况下，'that'也可以被'who'或'which '代替。
例如: That = Which
Tom bought the apples that the man was selling.
OR
Tom bought the apples which the man was selling.
例如: That = Who
Peter invited the boy that was new in class.
OR
Peter invited the boy who was new in class.
'That'可以用在充当动词宾语的从句中。
例子：
Jennifer hinted that she would be late for class.
Doug knew that he needed to hurry up.
The teacher suggested that we finish our homework.
'That'可以用在从句中，跟在名词或形容词后面作补语。补语有助于提供有关名词或形容词的附加信息。它回答了“为什么”的问题。
例如：
Peter is upset that his sister wants to drop out of high school.
Mr. Johnson appreciates our efforts that have brought in a lot of donations.
She is certain that her son will be accepted to Harvard.
That从句可以引入一个短语作为句子的主语。“that”从句的这种用法有点正式，在日常用语中并不常见。
例如
That it is so difficult is hard to understand.
That Mary feels so sad is very upsetting.
That our teacher expects us to do two hours of homework every day is crazy!
事实是……
与that从句作主语有关的是更常用的短语“the fact that…”来引出一个句子。虽然这两种形式都是正确的，但是用“the fact that....”开头的句子更常见。
例如
The fact that he wants to see you should make you happy.
The fact that unemployment is still high proves what a difficult economy this is.
The fact that Tom passed the test shows how much he has improved.
有很多与that连用的复合连词。这些表达通常在正式英语中使用，包括:
“in order that”“so that”“provided that”“in case that”“now that”“given that”
例如
He purchased the computer so that he might improve his typing.
Susan told him she would marry him providing that he found a job.
Alice feels happy now that she has moved into a new home.
在转述动词say (That)、tell someone (That)、regret (That)、imply (That)等后，可以省略That。
例如：
Jennifer said (that) she was in a hurry.
Jack told me (that) he wanted to move to New York.
The boss implied (that) the company was doing very well.
在回答“why”这个问题时，有些形容词后面可以跟“that”。'That'可以放在形容词后面。
I'm happy (that) you found a new job.
She's sad (that) he's going to move to New York.
Jack is anxious (that) he didn't pass the test.
当that作为从句的宾语时，省略它是很常见的。
He invited the boy (that) he met on the train.
Shelly purchased the chair (that) she had seen at the auction.
Alfred wants to read the book (that) Jane recommended.
