Wanting what someone else has and resenting them for having it is envy. If your best friend comes to school with the silver backpack you’d had your eye on all summer, you want to be happy for her, instead you feel bitter envy.
Envy comes from the Latin word invidere, which literally means “look upon.” You know when you say something funny or smart and someone gives you the evil eye? Envy all the way. Envy can be used as a noun or as a verb: Envy (noun) is the feeling you have when you envy (verb) what someone else has.