Transubstantiation

In Roman Catholic theology, transubstantiation (in Latin, transsubstantiatio, in Greek μετουσίωσις metousiosis) is the doctrine that, in the Eucharist, the substance of the bread and the wine used in the sacrament is changed into the substance of the Body and the Blood of Jesus, while all that is accessible to the senses (the appearances - species in Latin) remains as before.