CCC 1849 Sin is an offense against reason, truth, and right conscience; it is failure in genuine love for God and neighbor caused by a perverse attachment to certain goods. It wounds the nature of man and injures human solidarity. It has been defined as “an utterance, a deed, or a desire contrary to the eternal law.”1
1 St. Augustine, Contra Faustum 22: PL 42, 418; St. Thomas Aquinas, STh I-II, 71, 6.