You might be a beginner or have been learning French for a while and you’re still unsure about the correct French interrogative expression for ‘what’ or ‘which’. Que, quoi, quel(s), quelle(s) or qu’est-ce que (qui) ? Which one should you use?

Let’s try to clarify…
When ‘what’ precedes a noun, you need to use the interrogative adjective quel or quelle (f) in front of the noun. Quel(le) can be used with the inversion construction form or with est-ce que to make the question:

Quel animal vois-tu ? = Which/what animal do you see?

Quel animal est-ce que tu vois ? = Which/what animal do you see?

Quel(le) will also be used directly with the verb être (to be).

Quelle est votre destination ? = What is your destination? (Note that it is still an interrogative adjective and must agree with the noun).

Quel(le) can also be used as an exclamatory adjective – used for emphasis. In this instance, quel(le) is again followed by a noun and another adjective can also be used for further emphasis. Used this way it means ‘what’ or ‘what a’. Note that there is an exclamation mark at the end of the sentence:

Quelle histoire ! = What a story!

Quel bel homme ! = What a handsome man!

Que and its longer form qu’est-ce que are interrogative pronouns and are used as direct objects in a sentence. They are used to ask questions about things. As the object of a question, que may be followed by either inversion or with est-ce que.

Que préfères-tu ? = What do you prefer?

Qu’est-ce que tu préfères ? = What do you prefer?

Note:

A straight and simplified translation of ‘what do’ is qu’est-ce que…

The alternate form qu’est-ce qui is used when the “what” of your question is the subject of the sentence.

Qu’est-ce qui arrive ? = What’s going on, What’s happening?

Qu’est-ce qui fait le plus peur aux enfants ? = What is it that frightens children the most?

Use quoi when you have a preposition involved (à, de, dans, etc..) and the question can be formed either with inversion or with est-ce que.

A quoi pensez-vous ? = What are you thinking about?

Dans quoi mettez-vous le pain ? = What do you put the bread in?

De qui parlez-vous ? = Who(m) are you talking about?

Quoi can also be used for informal questions.

Tu fais quoi ? = You’re doing what? (instead of Qu’est-ce que tu fais ?)

Tu aimes quoi ? = You like what?

Be careful when “what” joins two clauses. In such cases, it is a relative pronoun and is used when whatever you are talking about is indefinite or uncertain. Do not use one of the above interrogatives, but use ce que, ce qui.

Je ne comprends pas ce qu’il dit ! = I don’t understand what he is saying!

Ce matin j’ai appris ce qui m’empêchait de dormir la nuit. = This morning I discovered what was preventing me from sleeping at night.