Choosing Between What and Which

Often, we put a noun right after a question word to ask for specific information (e.g., color, time, size). The biggest source of confusion for learners is choosing between what and which.

The rule depends on the number of possible answers:

• Use what + noun when there is an open, general, or unlimited number of possible answers.
• Use which + noun when you are asking someone to choose from a small, specific, or limited set of options.

✅ "What color is your new car?" (There are millions of colors in the world; the speaker has no specific list in mind.) ✅ "We have red and blue. Which color do you prefer?" (The choices are strictly limited to two options.) ❌ "We have red and blue. What color do you prefer?" (This sounds unnatural because the options have already been restricted.)

The edge case: Sometimes, what and which can both be correct, depending entirely on what the speaker is imagining. If a tourist asks, "What train goes to London?" they are thinking generally about all the trains in the country. If they ask, "Which train goes to London?" they are probably looking at a specific departures board with a set list of options right in front of them.

Asking About Quantity: How Much vs. How Many

When asking about quantities, we use how + much/many + noun. The rule here depends strictly on whether the noun is countable or uncountable.

• Use how many with plural countable nouns. These are things you can count with numbers, like cups, friends, books, or pancakes.
• Use how much with uncountable nouns. These are things you cannot count individually without a container or measurement unit, like coffee, time, money, or syrup.

✅ "How many cups of coffee did you drink today?" ❌ "How much cups of coffee did you drink today?"

✅ "How much time do we have before the train leaves?" ❌ "How many time do we have before the train leaves?"

The "How" vs "What" Trap

A very common mistake for B1-B2 learners is translating directly from their native language when asking about characteristics like size, color, or shape. In many languages, you use the equivalent of "how" for these questions. In English, we do not use how directly with a noun to ask about its type or identity.

If you are placing a noun directly after the question word, you generally need what or which.

✅ "What size shoes do you wear?" ❌ "How size shoes do you wear?"

✅ "What time does the rescue helicopter arrive?" ❌ "How time does the rescue helicopter arrive?"

✅ "What platform is for the express train?" ❌ "How platform is for the express train?"

Note: We do use "how" with adjectives (e.g., How big is it? How late are we?), but the moment a noun immediately follows the question word to ask for a specific category, what or which is the correct choice.