Cherub 2: Mom, Joshua knows the F word.
Me: (almost faint but calmly question him) Who is Joshua? What do you mean the F word? Do you know the F word?
Cherub 2: He is the one that bit me on the bus. He knows it. I don't. But I know it is bad. Is it bad?
Cherub 1: What is it?
Me: It's nothing. (Thankful neither seems to know it yet.) Yes, it is bad. So, what was your favorite part of the day?
(Yup, not so smooth transition to a new subject.)