"Bonne nuit mon garçon."

[Lord_Stanley]

Why do I use the feminine form of 'bonne' when referring to the subject of a boy? Should it not be the masculine form?

[jack.ryan]

it's referring to nuit/night, not boy

[u83rmensch]

why is the night feminine?

[Lord_Stanley]

Frequently I find it is best to not attempt to understand why things are masculine or feminine. Just accept it. For example, 'beard' and 'mustache' are both feminine, yet only* men can grow them.

*I understand the caveats needed when using words like only to describe facial hair.

[pedro_tex]

Why can't I use "evening"?

[fabpianista]

The use of "evening" is more convenient than "night" when we're coming to a place. When we are exiting, it's time to say "good night", I think.