Catechism of the Catholic Church §2539 — excerpt
Envy is a capital sin. It refers to the sadness at the sight of another's goods and the immoderate desire to acquire them for oneself, even unjustly.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: St. Augustine, De catechizandis rudibus 4, 8 PL 40, 315-316 · St. Gregory the Great Moralia in Job 31, 45: PL 76, 621