代词是用来代替名词的词。代词可以用作句子中的主语、直接宾语、间接宾语、介词宾语，可以代替任何人、动物、地方或事物。代词包括以下几种类型：人称代词，关系代词，指示代词，反身代词，疑问代词，物主代词。
代词的种类
| 代词的种类 | 代词的作用 | 代词的例子 |
|---|---|---|
| 人称代词 | 指代人、地点、事物或想法 | I, me, she, we, us, them, it, you, they |
| 关系代词 | 指代句子中的另一个名词，用以添加更多信息 | Who, whom, whose, which, that, when, where |
| 指示代词 | 指代已经提到的名词 | This, that, these, those, such, none, neither |
| 不定代词 | 指代未指明或非特指的名词 | Anybody, everybody, nobody, somebody, anyone, everyone, no one, someone, anything, everything, nothing, something |
| 反身代词 | 自指主语，作为句子的宾语使用 | Myself, yourself, yourselves, ourselves, himself, herself, itself, themselves |
| 疑问代词 | 用于发起问题，问的是关于某个特定名词的情况 | Who, what, which, whose |
| 物主代词 | 表示名词的所有权关系 | My, our, your, his, her, its, their |
人称代词
人称代词用于指代特定的语法人称，包括第一人称（I）、第二人称（you）、第三人称（he, she, it, they）。根据所指代名词的性别和数量等情况的不同，人称代词具有不同的形式。人称代词包括I, you, he, she, it, we they, me, him, her, us, them。
Example
She is clever.
Example
Did you make a reservation for three?
Example
I hope you will invite them to the party.
先行词
如果在句子中没有明确说明名词，代词对不同的人或事物的指代可能就不够清晰。当在句子中使用代词时，应当先使用先行词，让读者知道代词指的是什么。先行词是指在句子开头提到的名词或名词短语，它在句子的后面用代词代替。
Example
Sam drank most of the juice that he bought.
Example
The team has tried its best to achieve success.
Example
Many people lost their jobs because of the economic slowdown.
先行词不清晰的例子
Example
If you arrive late to the play, she won’t let you in.
Example
Sam sent a letter to Mark addressing the problems he encountered during his first year at school.
关系代词
关系代词用于连接关系分句和独立分句，以进一步描述相关的人或事物。关系代词直接放在它所修饰的名词或代词的后面。关系代词包括Who, whom, whose, which, that, when, where。
Example
Is the man who came to look for you your father?
Example
She likes books that tell stories of famous people.
Example
That store, where we usually buy our groceries, is closed for the holidays.
Who vs. whom：用作主语和宾语的代词
什么时候使用“who”或“whom”，有时会让人混淆。虽然这两个词都是代词，但它们的用法不同。“Who”用作句子的主语，而“whom”用作动词或介词的宾语。
Incorrect
Whom should be elected as the leader?
Correct
Who should be elected as the leader?
Incorrect
He is the person to who I am married.
Correct
He is the person to whom I am married.
Incorrect
You didn’t specify the officer who I should give this form to.
Correct
You didn’t specify the officer to whom I should give this form.
指示代词
指示代词用指句子中特定的人或物。这些代词也可以用来表示时间和空间的多少程度。指示代词包括This, that, these, those, such, none, neither。
Example
He is late again. That boy is really getting on my nerves.
Example
She loves all kinds of sports. These include badminton and soccer.
Example
I don’t like math or science. Neither is fun.
不定代词
不定代词用指不确定或泛指的人或物。与不定冠词类似，这些代词用来指代不确定的人或物。不定代词包括Anybody, everybody, nobody, somebody, anyone, everyone, no one, someone, anything, everything, nothing, something。
Example
No one likes to have to beg for something.
Example
Everyone is welcome to join the class.
Example
Anything is possible only if you keep trying.
反身代词
反身代词用于指代句子的主语。反身代词以“-self”（单数）或“-selves”（复数）结尾。反身代词包括Myself, yourself, yourselves, ourselves, himself, herself, itself, themselves。
Example
I saw myself in the mirror.
Example
The book itself isn’t difficult, but it’s not fun to read.
Example
They recommend this movie even though they have never seen it themselves.
疑问代词
疑问代词用于发起提问。疑问代词包括Who, what, which, whose。
Example
Which essay did you like the best?
Example
Whose bag is this?
物主代词
物主代词用来表示某人或某物对事物的拥有关系。物主代词包括My, our, your, his, her, its, their。使用这些代词可以避免重复用词，使句子更为简洁。
Example
I don’t know where my sneakers went, so my sister lent me her sneakers.
I don’t know where my sneakers went, so my sister lent me hers.
Example
Your plan sounds just as exciting as my plan.
Your plan sounds just as exciting as mine.