jealousy is the painful mix of fear, anger, and insecurity felt when a valued relationship, or the attention and affection it provides, seems threatened by a rival.
The word carries two older senses alongside the emotional one: vigilance in guarding something held dear — the "jealous God" of scripture, intolerant of rival devotion — and resentful hostility toward someone believed to enjoy an advantage. It entered Middle English from Old French gelosie, built on gelos, which traces through Late Latin to Greek zēlos, "zeal" — the same root as zealous, which is why the word has long connoted fierce attachment as much as suspicion.
Jealousy is routinely confused with envy. Envy involves two people: wanting what someone else has. Jealousy involves three: fearing the loss of what one already has to someone else. Researchers such as Bram Buunk further distinguish reactive jealousy, a response to an actual threat, from anxious and possessive forms that run ahead of any evidence. In 📝Consensual Non-Monogamy (CNM), jealousy is usually treated as information to explore rather than a verdict on the relationship, and the community's name for its emotional counterpart is 📝compersion — joy in a partner's happiness with someone else.