Friends with benefits

A relationship between friends which includes sex but no emotional attachment. Howard and Leslie were in a "friends with benefits" relationship, but Howard had strong feelings for her and when she ended the relationship, he was devastated.

Sheldon couldn't understand how that kind of relationship would work ("Does he provide her with health insurance?"). However, after chatting with Penny about it when he was forced to spend the night in her apartment, he told Leonard that he understood it much better.