We can use both ‘what’ and ‘which’ to ask questions. We can even use them interchangeably sometimes. However, these words are not always interchangeable, so you need to be careful. Check out our guide to using ‘what’ and ‘which’ in questions to ensure your writing is always error free.
What and Which in Questions
‘What’ and ‘which’ are interrogative pronouns. In other words, we can use these words in questions when we want someone to specify something:
What TV shows do you watch? ✓
Which TV shows do you watch? ✓
Here, for example, we’re asking someone to specify the TV programmes they enjoy. We can use either ‘what’ or ‘which’ in this case because the question allows a large – but finite – number of answers. In other cases, though, we would need to be more careful about the question word we used.
Open Questions vs. A Limited Range of Answers
The difference between ‘what’ and ‘which’ appears in questions that are either very open or fairly limited. When a question is broad, we use ‘what’:
What shall we do today? ✓
Which shall we do today? ✗
Here, ‘which’ would imply a limited range of choices. It would thus only be correct if, for instance, the preceding conversation has set out a limited number of choices (e.g. going to the beach or the cinema). ‘What’, on the other hand, leaves the question open to any number of answers.
We can reverse this by asking a question with a limited range of choices:
What hand do you write with? ✗
Which hand do you write with? ✓
In the sentence above, for example, ‘which’ is correct because the answer must be either ‘left’ or ‘right’. We also use ‘which’ before ‘of’ and ‘one’, as these terms also imply a limited set of possible answers:
Which of my hats do you like most? ✓
Which one should I wear? ✓
As such, if you are asking someone to specify one possible option out of a limited set of possible answers, you should always use ‘which’.
Summary: What or Which?
You can use both ‘what’ and ‘which’ in questions when asking for information that specifies something. Each term has a specific usage, though:
- Generally, when a question is open to many answers, it is better to use what. For example, asking What shall we do today? would imply that we are open to a large range of responses (not just a few pre-decided options).
- When a question is about a limited number of choices, use which. For instance, we would use this term to ask Which hand do you write with? because there are only two possible answers (left or right).
Hopefully, this has clarified how to use these terms. If you’d like a little more help getting ‘which’ and ‘what’ in order, though, just let us know.