Compersion

Etymology

A neologism generally attributed to the Kerista commune in San Francisco in the 1970s and 1980s, and later adopted by polyamorous communities. It has no classical roots and is an explicit coinage meant to fill a lexical gap — English had no positive counterpart to jealousy. Its spread beyond its subculture is recent.

noun · /kum-PUR-zhun/
The feeling of joy at another person’s happiness or pleasure, especially in a context where one might expect jealousy.
What it names
A handle for the warm, vicarious gladness that is the emotional opposite of envy — useful well beyond romance, for genuinely delighting in a rival’s or friend’s good fortune.
Example
When her co-author won the prize she had also been shortlisted for, she was surprised to feel compersion rather than resentment.
Related idea
It is roughly the inverse of schadenfreude (pleasure at another’s misfortune) and the opposite of envy; compersion takes joy in another’s good, not their harm.