Catechism of the Catholic Church
“The inexhaustible richness of this sacrament is expressed in the different names we give it. Each name evokes certain aspects of it. It is called:
Holy Communion, because by this sacrament we unite ourselves to Christ, who makes us sharers in his Body and Blood to form a single body. We also call it: the holy things (ta hagia; sancta) – the first meaning of the phrase “communion of saints” in the Apostles’ Creed – the bread of angels, bread from heaven, medicine of immortality, viaticum…”
Source: Catechism of the Catholic Church #1328-31