Difference between What and Which

Published on September 28, 2016

There are some people who are often confused with the usage of what and which in a sentence. Take a look at these examples:

  1. What food does your dog eat?
  2. Which food does your dog eat?

Both sentences are grammatically correct and too often, which and what are both possible. We need to know which one is more appropriate to use.

Definitions

What vs Which

What is a wh-word that is used to ask questions about things or action. It is also used as a pronoun and a determiner.

Examples:

I don’t know what to bring to Tricia’s party.

What is used as a pronoun and is used as a “thing.”

What a beautiful sight!

What is used as an exclamation to convey a high or intense viewpoint or emotion.

What is her problem?

In this case, what is used to form a direct question.

I was just wondering what her favorite movie was.

What works to form an indirect question in this example.

Which, like what, is also a wh-word used for asking questions. It is also used as a pronoun, adjective and for supplementary information.

Examples:

He had a problem choosing which of his proposals he should present.

In this example, which is used as a pronoun (referring to proposals).

Drive which way you want, you’ll still be able to get to your destination.

Which is used as an adjective.

The news, which appeared last night, affected her so much.

Which is used to add extra information.

What vs Which

What is the difference between what and which? Which and what are often used interchangeably and understandably so, because there is actually a slight difference of meaning between the two.

Which is used when the speaker knows that there is a limited number of choices, while what is used when there is an unknown number or limitless possibilities for an answer.

Examples:

Which is the correct answer?

This indicates that there a few options, and the question is pertaining to those options.

What is the correct answer?

This does not provide you any choice, and it could be anything that you have learned or studied.

Which movie is your favorite?

This suggests that the speaker and the listener already have a few movies in mind.

What is your favorite movie?

This conveys that it could be any movie from any time.

Comparison Chart

What Which
wh-words used to ask questions wh-words used to ask questions
Also used as pronouns Also used as pronouns
For a limited number of options For a limitless number of options

Video

The video below explains clearly the difference between what and which.