Catechism of the Catholic Church §1796 — excerpt
Conscience is a judgment of reason by which the human person recognizes the moral quality of a concrete act.
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.