Catechism of the Catholic Church §1566 — excerpt
"It is in the Eucharistic cult or in the Eucharistic assembly of the faithful (synaxis) that they exercise in a supreme degree their sacred office; there, acting in the person of Christ and proclaiming his mystery, they unite the votive offerings of the faithful to…
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: LG 28 · PO 2