复杂句是包含一个主句和至少一个从句的句子，从句需依附于主句才能构成完整意义。根据从句的功能和位置，复杂句主要分为以下类型：

一、名词性从句

主语从句

从句在句中作主语，例如：

What he said surprised everyone. [What] 作主语

Whether she will attend the meeting is still unclear. [Whether] 作主语

宾语从句

从句在句中作宾语，例如：

I believe that she is honest. [that] 引导宾语从句

The problem is whether we can finish the task on time. [whether] 引导宾语从句

表语从句

从句在句中作表语，例如：

The fact that he was late surprised everyone. [that] 引导表语从句

The reason for the delay is unknown. [The reason] 作主语，后续为表语从句

同位语从句

从句对前面名词进行解释说明，例如：

The book, which was written by him, is very popular. [which] 引导同位语从句

The man you saw yesterday is my friend. [you saw yesterday] 作后置定语，属于同位语从句

二、状语从句

时间状语从句

表示动作发生的时间，例如：

When she arrived, the meeting had already started. [When] 引导时间状语从句

Before the meeting started, we prepared the documents. [Before] 引导时间状语从句

地点状语从句

表示动作发生的地点，例如：

Where the meeting took place is unknown. [Where] 引导地点状语从句

Whenever we visit, we eat at the same restaurant. [Whenever] 引导时间状语从句

原因状语从句

表示动作发生的原因，例如：

Because of the rain, the match was canceled. [Because of] 引导原因状语从句

Since he was sick, he missed the meeting. [Since] 引导原因状语从句

条件状语从句

表示动作发生的条件，例如：

If it rains, we will cancel the picnic. [If] 引导条件状语从句

Unless you call me, the meeting will proceed. [Unless] 引导条件状语从句

让步状语从句

表示主句动作发生的让步条件，例如：

Although it was late, we still arrived on time. [Although] 引导让步状语从句

Even though he tried hard, he failed the exam. [Even though] 引导让步状语从句

三、其他特殊类型

非限制性定语从句

用逗号与主句分隔，对名词进行补充说明，例如：

The book, which I borrowed from the library, is very interesting. [which] 引导非限制性定语从句

名词性从句的省略

通过上下文省略引导词，例如：

I wonder if she will call you. [if 引导的从句省略了 that]

四、复杂句与简单句的区别

以上