Because it is “acheter qqc (à qqn)”.
https://www.lawlessfrench.com/grammar/verbs-with-a/
https://www.frenchtoday.com/blog/french-verb-conjugation/why-french-verbs-followed-preposition-a-infinitive/
Because it is “acheter qqc (à qqn)”.
https://www.lawlessfrench.com/grammar/verbs-with-a/
https://www.frenchtoday.com/blog/french-verb-conjugation/why-french-verbs-followed-preposition-a-infinitive/
To complement Maarten's answer with an example:
J'acheterai ce livre à mon frère. -- I am buying this book for my brother.
Je lui acheterai ce livre. -- I am buying this book for him.
Don't have an account yet? Join today
Test your French to the CEFR standard
Find your French level