How did the Fourth Lateran Council define transubstantiation in 1215?

The Fourth Lateran Council, held in 1215, did not invent the concept of transubstantiation, but it formally sanctioned the term as the correct expression of Eucharistic doctrine.12

By officially adopting this terminology, the council provided a definitive framework for understanding the real presence of Christ in the bread and wine. This definition established that while the empirical appearances of the elements remain unchanged, their underlying substance is transformed into the body and blood of Christ.31

This conciliar action paved the way for later Scholastic theologians, such as St. Thomas Aquinas, to further elaborate on the doctrine using Aristotelian concepts, distinguishing between the "substance" that changes and the "accidents" (outward appearances) that persist.2