This is your resident Thomist bringing you a minute from the Bellowing Ox.
Have you ever wondered why there are various names for the Eucharist? We hear it called, “Sacrifice” “Eucharist,” “Communion,” and “Viaticum.” Aquinas relates that the various names are fittingly applied because they all signal some significant meaning for the Eucharist.
It is called “sacrifice,” he says, for its significance as a commemoration of our Lord’s brutal death. Sacrifice refers to the past tense. When the priest lifts the host, he is offering to the Father the only perfect and infinite sacrifice. He is appeasing divine justice with Christ’s sacrifice.
The Eucharist is called “Communion” in correlation to the present tense. By communion, it represents the unity of the mystical body of Christ. We become one body through reception. In this sense, it makes one question those who are not in unity with Catholic doctrine, yet portend to deserve the Eucharist. (No one “deserves” it.)
Finally, Thomas says the future tense is “viaticum” as it awaits with expectation fruition or paradise. The term Eucharist he assigns to the future tense as well because it means “good grace”, or points to heavenly fruition.