One of the common questions my editing clients ask me is, "What's the difference between envy and jealousy? Which word should I use?"
The two words describe slightly different emotional states, but sometimes it's hard to tease them apart. I like to put it this way: Envy says, "I want this to be me also." Jealousy says, "I want this to be me instead."
In other words, envy means you look at someone else and you wish you also had whatever they have (that great job, that fabulous suit, that gorgeous lover). In envy's ideal world, the end situation would involve both of you having the thing you're envious about.
Jealousy is a little different. It involves a feeling that the other person has something that should be yours; in other words, you think you should have that great job or fabulous suit or gorgeous lover and they shouldn't. Jealousy says, "They have something that's rightfully mine." In jealousy's ideal world, you would have the thing you're jealous about and the other person wouldn't.
There's a big difference between the two in terms of how the emotion drives motivation, and this is important if you're writing characters who experience either envy or jealousy. If your character is envious, that might motivate them to work hard to achieve similar results on their own. But if your character is jealous, that might motivate them to try to take away whatever the other person has, since jealousy says, "That should be mine and not yours."
So which one does your character experience: envy or jealousy? And where does that lead your story?