疑问词通常被归类为代词，用于代替名词或名词短语来提出问题。主要的疑问词包括Wh-代词（如what、who、whom、whose、which、where、when、why、how等）、whether以及Yes/No问句。它们通常被用作疑问句的开头，帮助我们获取所需的信息。
疑问词通常被归类为代词，因为它们用于代替一个名词或名词短语来发问。疑问词可以分为以下几类：
1. Wh-代词
Wh-代词是最常用的疑问词，它们包括：what、who、whom、whose、which、where、when、why、how等。这些词用于询问各种问题，如：
- What do you like to eat?
- Who is your favorite singer?
- Whom did you talk to on the phone?
- Whose book is this?
- Which color do you prefer?
- Where do you live?
- When is your birthday?
- Why are you crying?
- How do you spell your name?
2. Whether
Whether一般被认为是一种连词，但它也可用作疑问词，表示“是否”。例如：
- I don't know whether he is coming or not.
3. Yes/No 问句
Yes/No 问句是指用“是”或“否”回答的问题，但它们也可以被视为疑问词。这些问题通常以助动词或情态动词开头，如：
- Can you swim?
- Have you eaten breakfast?
- Is it raining outside?
- Should I call you later?
- Will you come to the party tonight?
