Vocabulary: 'Conflating'

I was just reading  Helen and Sharon this morning—I know, I'm weird that way—and came to a paragraph where Helen tells James that Megan is his 'sister', (in this story, he's only three) but he contradicts his mother, and says no, Allie is his sister.  Helen thinks: man, I screwed that one up; clearly James was conflating sister and girl.

Conflation is an interesting and useful idea.  When someone conflates two words—like 'sister' and 'girl', as James might be doing—it's a lot like confusing the two words: sometimes the two words do mean the same thing, but the two words usually are intended to mean different things.