The lexicon of dating is a complicated affair. There are subtle differences and nuances—and no one has it straight. You might be “going out” with someone and never really go anywhere besides the video store. You might be “seeing someone” you rarely see. When dating, we are loath to label things too early so we use these vague metaphors to skirt around the issue. Nevertheless, there comes a time in every romantic relationship when you have to define things, when you must awkwardly match words to the murky negotiations of two people who like to go out for drinks together and kiss. This is not only about pointing out the elephant in the bedroom—acknowledging that you are in fact “more than friends”—but it is also a practical necessity. What do you call this new person in your life? “Where’s your boyfriend tonight?” friends ask. “He’s ...