Relative pronoun lequel
Summary
Lequel (laquelle, lesquels, lesquelles) is the relative pronoun used after a preposition, agreeing in gender and number with its antecedent and contracting with à and de.
Explanation
lequel and its forms laquelle (feminine), lesquels (masculine plural) and lesquelles (feminine plural) are relative pronouns used after a preposition. They agree in gender and number with the antecedent: la chaise sur laquelle je suis assis (the chair I'm sitting on), les outils avec lesquels il travaille (the tools he works with).
For a human antecedent after a preposition, French normally prefers qui: la personne avec qui je parle (the person I'm talking to) is more natural than avec laquelle. lequel is the default for things and is also used for people to avoid ambiguity or in more formal style.
lequel contracts with the prepositions à and de. à + lequel = auquel, à + lesquels = auxquels, à + lesquelles = auxquelles (but à + laquelle stays as à laquelle). Likewise de + lequel = duquel, de + lesquels = desquels, de + lesquelles = desquelles, while de + laquelle stays as de laquelle. The plain forms à lequel and de lequel never exist.
There is a clear division with dont. For a simple complement in de, French uses dont, not de + lequel: le livre dont je parle, not le livre duquel je parle. The duquel / desquels forms appear mainly inside compound prepositions ending in de — à côté de, près de, au milieu de — as in la maison à côté de laquelle je vis (the house I live next to).
Two pitfalls dominate. First, forgetting to contract: it is auquel, not à lequel, and duquel, not de lequel. Second, choosing lequel where dont is required: with a verb that simply takes de (avoir besoin de, parler de), use dont. Use the lequel family specifically after other prepositions (sur, avec, pour, sans, dans…) and inside compound de-prepositions.
Rule of thumb: after a preposition, pick the lequel form that matches the antecedent's gender and number; switch to qui for people; collapse à and simple de into auquel/duquel; and reserve plain dont for the simple de cases.
Examples
Voici le stylo avec lequel j'ai signé le contrat. — Here is the pen with which I signed the contract. (avec + lequel (masculine singular thing).)
C'est une question à laquelle je ne peux pas répondre. — It's a question I can't answer. (à + laquelle stays uncontracted; répondre à takes à.)
Ce sont des projets auxquels je tiens beaucoup. — These are projects I care a lot about. (à + lesquels = auxquels; tenir à takes à.)
La personne avec qui je travaille est en vacances. — The person I work with is on holiday. (For people after a preposition, qui is preferred over laquelle.)
La maison à côté de laquelle je vis est ancienne. — The house I live next to is old. (Compound preposition à côté de keeps de laquelle (not dont).)
Common mistakes
C'est un projet à lequel je pense souvent.
C'est un projet auquel je pense souvent.
The preposition à contracts with lequel and its plural forms: à + lequel = auquel, à + lesquels = auxquels, à + lesquelles = auxquelles (but à + laquelle stays uncontracted). The forms à lequel / de lequel never occur. The same happens with de: de + lequel = duquel, de + lesquels = desquels.
Prerequisites
Related rules
pronounsrelative-clausesprepositionscontractions