"Mom. Is S-P-X a swear word???" Me: "S-P-X?" Her: "Yes." Me: "Nooo..." Her: "So, 'sex' isn't a swear word?" Me: "Oh. s-e-x. Um, no, it's not really a swear word. It's just one of those words we don't really need to have discussions about at this age." Her: "'Cause I read something about, "..dog's sex..." Me...and 12 y.o.: "Oh...in that sense it's gender. Like, is it a boy or a girl."
Later. Her: "Mom. Holli told me that 'sex' is a swear word." *Back to that again* Me: "Well, there is another meaning to that word that I will have to...uhhh...try to figure out at some time how to explain to you. But you really don't need to know much about that meaning quite yet!"
Oh these enlightening conversations you're never quite prepared for!