And that's when they're used in relative clauses to introduce adjective clauses.

那就容词性的定语从句里面。

This one, however, we're adding more information in this relative clause here.

然而，我们这系从句中添加了更多的信息。

We use them in relative clauses too.

我们也系从句中使用它们。

This is where we come to adjective clauses, also called relative clauses.

这就我们要讲的容词从句，也叫系从句。

When the relative pronoun represents the object of the relative clause, such as in sentences b) and d) , it can be left out.

当系代词指定了定语从句中的宾语，比如第二句和第四句，它就可以被省略。

But, 'that' can only be used in what we call identifying relative clauses and those are clauses where you need the information to understand what you're talking about.

但，That只能用于我们所谓的身份辨识分句中，而这种分句能提供信息来帮助别人理解你正谈论的内容。

The " he can't refuse" part of the sentence is a relative clause. It is modifying, or changing the meaning, of the noun " an offer."

句中 “he can't refuse” 系从句。它对名词 “an offer” 进行修饰或改变其含义。

Another common structure is relative clauses, using relative pronouns like who, which or what to link two clauses.

另常见的结构系从句，使用系代词，如“who”、“what”或“what”来连接两从句。

There is the clauses, so a mixture of subordinate dependent or non dependent clauses, relative clauses.

有从句，由从属从句或非从句、系从句混合而成。

We discussed relative clauses in an earlier Everyday Grammar story.

我们之前的每日语法已讨论了系从句。

A relative pronoun is used to connect a relative clause to the rest of a sentence.

系代词用来连接系从句和句子的其余部分。

The relative clauses here all begin with 'who' or 'whose'.

这里的系从句都以 who 或 whose 开头。

Now, 'that' is less formal, and it can be used for both people and things in some relative clauses.

That的用法稍微有点不正式。些系分句中，它可以同时用来修饰人和物。

Now these words are exactly what we're going to talk about today, 'which' or 'that' in relative clauses.

这两单词就我们今天要讨论的内容啦，系从句中的‘which’或‘that’。

The last relative pronoun " what" can also be used in relative clauses, but it is different.

最后系代词 “what” 也可以用于定语从句中，但它比较特别。

So for example, I'm living in London which is a beautiful city. Relative clause, two clauses.

I'm living in London which is a beautiful city.系从句，两从句。

Defining relative clauses such as these specify which noun we are talking about.

像这些句子就限定性定语从句了，限定了我们所讨论的名词哪。

Relative clause, adjective clause, what are we talking about? That sounds confusing!

系从句，容词从句，我们说什么呢？完全听不懂啊！

Relative clauses are another useful topic if you want to improve your sentence grammar.

如果你想提高你的句子语法水平的话，系从句另非常有用的话题。

Thirdly, don't use relative clauses, with who, which, that, where, etc. , unless it's really necessary.

第三，不要用 who、which、where 等引导系从句，除非真的很有必要。