ESEN
Which one to use?Intermediatepronounpronoun
WhatvsWhich
'What' asks from an unlimited set of options; 'which' asks when there is a limited, defined set of options to choose from.
Side-by-side comparison
What
pronoun"What" is used when the number of options is open or undefined. You are asking about something without limiting the universe of possible answers.
What would you like to eat tonight? I can cook pasta or order something in.
What time does the library close on Fridays? I need to return a book today.
What did she say when you told her about the surprise party this weekend?
Which
pronoun"Which" is used when the number of options is limited and defined. You are choosing within a specific and known set.
We have chocolate and vanilla ice cream. Which one do you prefer?
Which of these two films do you want to watch first, the comedy or the thriller?
Which seat would you like on the flight, the window or the aisle?
Common mistake
- •The most common error: using "which" for open options ("Which is the best city?" should be "What") or "what" for a defined set.
- •In informal contexts, native speakers often use both interchangeably, the distinction matters most in formal written English.
Trick to remember it
- •Set test: do the possible options form a limited, already-known group? Yes = "which" (closed set); no = "what" (open set).
- •Signal for "which": when the group of options has already been mentioned ("here are three candidates, which one?").
Quick rule
- •What = open choice (unlimited or unknown options).
- •Which = choice within a limited, known set.
- •"What is your favorite color?" (unlimited).
- •"Which do you prefer, red or blue?" (limited to 2).
Did you know?
The WHAT vs WHICH distinction reflects what logicians call "open vs closed domain reference." WHAT = open domain (any possible answer). WHICH = closed domain (an already-defined subset). Spanish uses "qué" and "cuál" similarly but with slightly different rules: "¿cuál es tu color favorito?" (cuál = which, slightly more formal in Spanish) vs "¿qué color te gusta?" (qué = what). The cuál/qué rules in Spanish are not identical to which/what in English, generating transfer errors. In particular, Spanish more freely accepts "cuál" where English requires "what."
Practise what you learned
Exercise 1 · Pick the right one
_____ is your favourite colour? I'm trying to choose a present for you.
Exercise 2 · Pick the right one
_____ one do you prefer — the red shirt or the blue one?
Exercise 3 · Form the word
Related word pairs
HowvsWhat
'How' asks about manner, degree, or process; 'what' asks about a thing, identity, or content.
How muchvsHow many
'How much' asks about uncountable nouns; 'how many' asks about countable nouns.
WhichvsWho
'Which' is used for things, animals, and concepts; 'who' is used for people.
AvsAn
'A' is used before consonant sounds; 'an' is used before vowel sounds.
Bryan López
Founder of SpeakUP Academy