Catechism of the Catholic Church §191 — excerpt
"These three parts are distinct although connected with one another. According to a comparison often used by the Fathers, we call them articles. Indeed, just as in our bodily members there are certain articulations which distinguish and separate them, so too in this profession of…
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: Roman Catechism I, I, 4 · St. Ambrose, Expl. symb. 8: PL 17, 1196