Compersion

Compersion is love manifested when a person takes joy in his or her loved one's happiness with another person. It is a form of empathy; that is, pleasure that a loved one is experiencing a good thing in his or her life. It need not be sexual. This distinguishes it from erotic excitement in watching another person or persons behaving sexually, known as voyeurism.

Feeling compersion for the first time is sometimes described as frightening and disorienting because it runs contrary to the jealousy most cultures believe one is likely to feel in such circumstances.

The term was coined by the Kerista Commune in San Francisco which practiced polyfidelity, and is one of the core values of polyamory.

The adjective frubbly is used in the United Kingdom to describe the feeling of compersion.