Transubstantiation

Transubstantiation (Latin: transubstantiatio; Greek: μετουσίωσις metousiosis) is a Roman Catholic doctrine regarding the Eucharist. The Roman Catholic Church teaches that "[t]he Eucharist is the very sacrifice of the Body and Blood of the Lord Jesus which he instituted to perpetuate the sacrifice of the cross throughout the ages until his return in glory" (https://www.vatican.va/archive/compendium_ccc/documents/archive_2005_compendium-ccc_en.html, 271). Transubstantiation is specifically the idea that the Eucharist (see Lord's Supper) literally becomes the Body and Blood of Jesus when the priest blesses it (https://www.usccb.org/eucharist, https://www.catholiceducation.org/en/culture/catholic-contributions/transubstantiation.html, https://archive.org/details/workscunn03cunn/page/142).