Learn French: Au revoir, Madame. Bonne journée ! - Goodbye, madam. Have a good day!

Jour refers to the day as a simple unit of time, which is why it is used in the standard greeting bonjour (hello). Journée emphasizes the length and experience of the day. When you wish someone a good experience for the rest of their day as they leave, you use bonne journée.

Why is it bonne journée and not bon journée?

In French, describing words (adjectives) have to match the gender of the noun they describe. The word journée is feminine, so the masculine word bon (good) changes to its feminine form, bonne.

The English translation says "Have a good day!", but where are the words for "have" and "a"?

You don't need them! In French, it is perfectly polite and natural to just say Bonne journée ! (literally "Good day!") when parting ways. You don't need to add a verb like "have" to make it a complete wish.

What does au revoir literally mean?

It literally means "to the seeing again." Au means "to the" and revoir means "to see again." It is the French equivalent of saying "until we meet again."