Here's why:
* "Vacances" is a plural noun in French, meaning "holidays" or "vacation."
* "Bonnes" is the feminine plural form of the adjective "bon," meaning "good."
Therefore, you need to use the feminine plural form of the adjective to agree with the plural noun "vacances."
So, the correct phrase is "bonnes vacances" which translates to "good holidays" or "happy vacation."