Which vs. what



What is the best way to explain the difference between which and what in questions, as in:

(a) Which color are your shoes?

(b) What color are your shoes?

Marķa Antonieta


You almost answered your own question when you wrote: "What is the best way to explain.?" What is used to ask a question when there are an unknown number or infinite possibilities for an answer. You know that there are many, many ways that exist to address your question, and you want to find out—from all those possibilities that you might not even know about—what the best way is.

(In “What is the best way to explain…?,” what is a question word. In your question about shoes, what and which are determiners used before nouns – “shoes,” in this case.)

In answer to your question about shoes, you would most likely ask what color, not which color, if you haven't seen the shoes yet and you want the owner of the shoes to tell you the color. This is because there are so many possibilities that the color of the shoes could be.

But, you would probably use which color if you are choosing between two items, already defined, in a different sentence, like this:


Which color shoes should I wear with this dress—blue or black?


Which shoes should I wear with this dress—my blue ones or my black ones?

You can use which when you have a very small or limited field to choose from. Certainly use which, not what, when there are only two choices, or if both speaker and listener can visualize all the items under consideration:


Which foot did you break?


Which one of your sisters is the singer?


Which of the restaurants is open on Sunday?



Which movie do you want to see?

Sentence (f) asks for information about the time or theater or title of a movie when you are selecting from only a few choices, known to both the speaker and listener: perhaps the time (4:45 p.m., 7:30 p.m., or 10:00 p.m.), or the theater (the Plaza Theater, the Cinemaplex, or the AMC theaters), or the movies that are playing in town. If you don't have any idea of how many movies there are in the discussion you are having, if you are thinking of all the possible movies, you would say:


What movie did you see last night?


What was Anthony Quinn's last film?

Often, either which or what can be used for several choices, depending on what is in the speaker's mind:


Which bus goes downtown?


What bus shall I take?

Both sentences are fine. The speaker is probably thinking about fewer buses in sentence (i) than in sentence (j). Similarly,


Which country in Europe is he from?


What country in Europe is he from?

are both OK.

However, you would probably want to say


What country is he from?

when you are not limited to one area because there are many, many choices of countries in the world, and probably more countries than you know of. You'd also say:


What language does he speak?

because there are so many languages in the world, and you don't know what all of them are.

However, you could very well say


Which language does he speak?

if, for example, his mother speaks French, his father speaks Italian, and the family lives in Brazil—in this case, there are only three clear possibilities.

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