The French language is full of exceptions and nasty rules when it comes to its grammar and orthography. This series of posts will give you some tricks to remember them quite easily.
This little trick will help you figure out when to use leur, and when to use leurs.
Leur (them) is the plural form of lui (him), while leurs (their) is the plural form of ses (his).
To get a gist of which form to use, you can replace leur or leurs by either lui or ses and see which sounds better.
“Je leur ai offert un cadeau” (I have offered them a gift), would give either “Je lui ai offert un cadeau” (I have offered him a gift), which sounds correct, hence you should use leur in this example, or “Je ses ai offert un cadeau” (I have offered his a gift), which is semantically and grammatically wrong.
French grammar trick #1: a or à?
French grammar trick #2: One or two Rs?
French grammar trick #3: Où or ou?
French grammar trick #4: Which adjectives are placed before their noun in French?
French grammar trick #5: être or avoir?
French grammar trick #6: Past participle or infinitive?
Don’t forget to upvote this post if you would like me to present other French grammar tricks, and leave a comment if you want me to deal with a specific grammatic point.
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