I SOMETIMES slip and call my ex-husband “my husband.”

It’s a bad habit, and a little embarrassing, this lack of clarity. Especially because our breakup was brutally clear: one night nearly six years ago, Chris looked at me from his usual spot on the sofa and said, with a wave of his hand, “I’m done with this.”

There were no months of trying to save our decade-long marriage. No tortured fights about staying together for the sake of our 10-month-old son. He simply waited an appropriate grace period from his first pronouncement — waiting for me to be done trying, as he put it — then packed his things and moved out.

And yet, he never really left. Two or three nights a week when I come home from work or an evening out, Chris is sitting at my dining room table, eating dinner or working at the computer, having entered with his own key and having made himself at home in the apartment that my son and I moved into after the divorce. If he orders food, he’ll sometimes get me my favorite nachos. He set up my computer system so that I have wireless access throughout the apartment (which works for him as well, of course). He installed my stereo and advises me on all electronic purchases. And when I go away on business trips, he moves back in, for four or five days at a time, to take care of our son.

His toothbrush sits in my toothbrush cup. Next to my boyfriend’s toothbrush.

You can see how things sometimes get confusing.