Lequel is one of the most difficult French pronouns because it has four forms that must agree in gender and number with the noun it replaces. Lequel can be either an interrogative pronoun, replacing "quel" and a noun when asking a question, or a relative pronoun replacing an inanimate object introduced by a preposition. It has several contracted forms when used before à and de, and its different forms are shown in a table according to its gender and number.

1. Lequel

2. Lequel
Lequel, which usually means which, is arguably the most
difficult French pronoun.
Lequel has four basic forms, because it has to agree in gender
and number with the noun it replaces.
In addition, lequel has several contracted forms - like the
definite articles le and les, lequel contracts with the prepositions
à and de. You can see all of these forms in the table below.
Lequel is usually either an interrogative pronoun or a relative
pronoun.

3. Lequel
Interrogative pronoun: Lequel replaces quel + noun.
• Quel livre veux-tu ? > Lequel veux-tu ?
• Which book do you want? > Which one do you want?
• Je veux la pomme là-bas. > Laquelle ?
• I want the apple over there. > Which one?
• Je pense à mon frère. > Auquel penses-tu ? [À quel frère...]
• I'm thinking about my brother. > Which one are you thinking about?

4. Lequel
Relative pronoun: Lequel replaces an inanimate object of a
preposition. (If the object of the preposition is a person, use
qui.)
• Le livre dans lequel j'ai écrit...
• The book in which I wrote...
• La ville à laquelle je songe...
• The town about which I'm dreaming...
• Le cinéma près duquel j'ai mangé...
• The theater near which I ate... / The theater I ate near...

5. Singular
Masculine
Forms
à+
lequel
de +
lequel
Feminine
Plural
Masculine Feminine
lequel
laquelle
lesquels
lesquelles
auquel
à laquelle
auxquels
auxquelles
duquel
de
laquelle
desquels
desquelles