Six in French

Sumner: Mom, do you know what six in French is?

Me: No.

Sumner: Just replace the i with an e.

Me: Sex?

Sumner: (with a grin) Yeah.

Me: What is sex anyway?

Sumner: I think it is a swear.

Me: No, it's not.

Sumner: Then it must be a potty word.