Let's say a guy named Roger is attracted to a woman named Elaine.
He asks her out to a movie; she accepts; they have a pretty good time.
 
A few nights later he asks her out to dinner, and again they enjoy themselves. They continue to see each other regularly, and after a while neither one of them is seeing anybody else.


Then, one evening when they're driving home, a thought occurs to Elaine, and, without really thinking, she says it aloud: "Do you realize that, as of tonight, we've been seeing e...