Not To Be Confused With
Transubstantiation (substance changes, accidents remain — a specific philosophical account) is the Catholic explanation; Lutherans hold sacramental union, the Reformed a spiritual real presence, and memorialism denies any change. All but the last affirm “real presence.”
Defined at the Fourth Lateran Council (1215) and Trent, using Aristotelian categories of substance and accident. It is one explanation of real presence, not a synonym for it — presented here in the Catholic Church's own voice.