In the singular, the form changes according to the gender of the noun. With a masculine singular noun, we use quel : Quel train part à huit heures ? With a feminine singular noun, we use quelle : Quelle rue mène à la gare ? The interrogative adjective therefore agrees with the noun it accompanies, as in Accord de l'adjectif. The noun remains always singular when the question concerns one person or one thing.

In the plural, the gender still matters. With a masculine plural noun, we write quels : Quels films veux-tu voir ? With a feminine plural noun, we write quelles : Quelles villes visiterez-vous ? The form of the interrogative adjective follows the noun, like the other adjectives studied in Formation de l'Adjectif. If the noun is plural, the interrogative adjective also takes the plural, even in a very short question.

Forms according to gender in the plural

Idea
We use which with a masculine plural noun.
We use which with a feminine plural noun.

The interrogative adjective always comes before the noun it accompanies. We say Quel parfum choisis-tu ? and not parfum quel. The question is built with adjective + noun + verb, or with adjective + noun + another element of the noun phrase. When the adjective introduces the group, it functions like the other adjectives placed before the noun in certain cases, depending on their use and their place described in Position de l'adjectif.

Placement before the expressed noun

Idea
On emploie quels avec un nom masculin pluriel.
On emploie quelles avec un nom féminin pluriel.

With être, the question asks an identity, a profession, an opinion or a category. We say Quel est ton nom ?, Quelle est sa profession ?, Quels sont leurs projets ? In speech, the structure can remain simple with intonation, or take est-ce que : Quel est ton numéro ? or Quel est-ce que tu préfères ? With a proper name, quel is used to ask which element among several we are talking about: Quel Paris connais-tu, celui d’hiver ou celui d’été ? The usage remains that of an interrogative adjective, as with the other forms studied in Adjectifs démonstratifs when one wants to designate a noun precisely, but here the question replaces the designation with a choice to identify.

Usage with être

Usage	Explanation
Question with être	Use which before the verb to be to ask to identify a subject or property.
Question avec personne ou objet connu	On utilise quel devant un nom déjà visible dans le contexte pour demander une précision sur cette personne ou cet objet.

With être, the question asks for an identity, a profession, an opinion or a category. We say Quel est ton nom ?, Quelle est sa profession ?, Quels sont leurs projets ? In speech, the structure can stay simple with intonation, or take est-ce que : Quel est ton numéro ? or Quel est-ce que tu préfères ? With a proper noun, quel is used to ask from which element among several we are talking about: Quel Paris connais-tu, celui d’hiver ou celui d’été ? The use remains that of an interrogative adjective, as for the other forms studied in Adjectifs démonstratifs when we want to designate a noun precisely, but here the question replaces the designation with a choice to identify.