leur vs leurs
Summary
leur has two grammatical lives: as an indirect-object pronoun before a verb it means "(to) them" and is invariable (never *leurs), while as a possessive adjective before a noun it means "their" and takes -s when the noun is plural (leur maison, leurs enfants).
Explanation
The single form leur does two unrelated jobs, and only one of them can ever take an -s. Sorting them out is a matter of asking what leur is sitting next to: a verb or a noun. That one question settles both the meaning and whether an -s is allowed.
Job one: leur as an indirect-object pronoun. Placed before the verb, it replaces "to/for them" (à eux / à elles): Je leur parle (I talk to them), Il leur a donné un cadeau (he gave them a gift), Nous allons leur écrire (we're going to write to them). In this role leur is invariable: it stays leur no matter how many people are meant, because a pronoun does not agree in number the way a possessive does. Writing *je leurs parle is always an error.
Job two: leur / leurs as a possessive adjective. Placed before a noun, it means "their" and agrees with the thing possessed, not with the owners: leur maison (their house (one house), leur voiture (their car), but leurs enfants (their children) several), leurs idées (their ideas). Since the owners are always plural ("they"), only the number of the possessed noun decides between leur and leurs.
There is also a possessive pronoun built on the same root: le leur, la leur, les leurs ("theirs"). It replaces "their + noun" and agrees with that noun's gender and number: Ma voiture est rouge, la leur est bleue (mine is red, theirs is blue); Nos enfants et les leurs (our children and theirs). Here the article (le/la/les) already signals the number, and leurs takes -s in the plural.
The traps for English speakers are two, and they pull in opposite directions. First, adding -s to the pronoun: because "them" feels plural, learners write *je leurs téléphone; but the verb-side leur never varies. Second, failing to agree the possessive: writing *leur enfants for several children; the noun-side leur must become leurs before a plural noun. English "their" is invariable, so English speakers under-mark the plural on the possessive and over-mark it on the pronoun.
Rule of thumb: is leur touching a verb? Then it is the pronoun "(to) them" (always leur, no -s. Is leur touching a noun? Then it is the possessive "their") add -s only if that noun is plural (leur / leurs).
Examples
Je leur téléphone ce soir.I'm calling them tonight.Indirect-object pronoun before the verb -> invariable leur, no -s.
Leur maison est au bout de la rue.Their house is at the end of the street.Possessive before a singular noun -> leur.
Leurs enfants vont à la même école.Their children go to the same school.Possessive before a plural noun -> leurs; the owners' number is irrelevant.
Nous allons leur offrir des fleurs.We're going to give them flowers.Pronoun before the infinitive -> leur, still invariable.
Ma chambre est petite ; la leur est immense.My room is small; theirs is huge.Possessive pronoun la leur agreeing with chambre (feminine singular).
Je leur ai rendu leurs livres.I gave them back their books.Both in one sentence: pronoun leur (invariable) + possessive leurs (plural noun).
Common mistakes
Je leurs parle tous les jours.
Je leur parle tous les jours.
Before a verb, leur is the indirect-object pronoun meaning "(to) them", and it is invariable: it never takes an -s, no matter how many people are involved. Adding -s (« je leurs parle ») confuses it with the possessive adjective leurs (« their », as in leurs amis), which only appears before a noun and agrees with that noun. The decision rule: leur touching a verb = pronoun, always leur; leur touching a plural noun = possessive, leurs.
Related rules
Sources
- « Les homophones leur et leur(s) », Vitrine linguistique de l'Office québécois de la langue française
pronounspossessivesagreementconfusables