Relative clause（关系从句）
关系从句帮助定义或告知我们关于我们正在谈论的事情或人的额外信息。
关系从句以关系代词（who, which, that, whose, whom）或关系副词（where, when, why）开头。
关系代词/副词 | 含义 |
who | 指代人 |
which | 指代事物或动物 |
that | 指代人、动物、事物(可以替代which或who，用于非正式场合) |
whose | 指代所有关系 |
whom | 指代人，who是宾语时替代 |
where | 指代地点 |
when | 指代时间 |
why | 指代原因 |
句型
关系从句 | |
句型1 | 关系代词/副词 + 主语 + 动词 |
示例 | The present which he gave me was just amazing. |
That memorable moment was the time when he kissed me for the first time. | |
Jack sent me a job offer that I couldn’t decline. | |
句型2 | 关系代词作主语 + 动词 |
示例 | The girl who is standing next to John is my younger sister. |
Venus flytrap is a plant which traps insects. | |
Henry is a man who is very kind and friendly. |
有两种关系从句：限定性关系从句和非限定性关系从句。
1. 限定性关系从句
限定性关系从句会添加有关所定义的特定名词的详细信息。它们提供了关于所指人、事物的重要信息。
如果没有限定性关系从句，其含义会改变。
Venus flytrap is a plant which traps insects.
This was the evidence which greatly affected the case.
I am going to show you a video which was made by the most famous American film director.
注：
代词who在口语中可以用that替代。
在限定性关系从句前不使用逗号。
Venus flytrap is a plant which (that) traps insects.
Venus flytrap is a plant, which traps insects.
This was the evidence which (that) greatly affected the case.
This was the evidence, which (that) greatly affected the case.
2.非限定性关系从句
非限定性关系从句提供了关于人或事物的额外/非必要的信息。它并不影响整个句子的含义。
没有限定性关系从句，含义保持不变。
Mr. David, who is an inspiring teacher, won the Global teacher prize 2018.
I’ve just come back from England, which is a very beautiful country.
My two puppies, which were only 6 days old, are taken care of very carefully.
注：
非限定性关系从句不使用that。
一般在非限定性关系从句前使用逗号。
Mr. David, who is an inspiring teacher, won the Global teacher prize 2018.
Mr. David that is an inspiring teacher, won the Global teacher prize 2018.
I’ve just come back from England, which is a very beautiful country.
I’ve just come back from England which is a very beautiful country.
语录网网友观点：搞成定语从句不是更好理解吗？非得要搞成关系从从句。
也可以叫定语从句，但从英文来看，叫关系从句可能更为妥当一点。