Definition of liturgy:
(a particular set of) the words, music and actions used in ceremonies in some religions, especially Christianity. Etymology: from from Middle French liturgie, from Classical Latin liturgia "public service, public worship," from Greek leitourgia, from leitourgos "one who performs a public ceremony or service, public servant"
Definition of communion:
From Old French communion, from Classical Latin communionem (nom. communio) "a sharing," used in Late Latin ecclesiastical language for "participation in the sacrament," from communis (see common). Used by Augustine, in belief that the word was derived from com- + unus "oneness, union."
Jesus' teaching on communion:
Matthew 26: 26-28
While they were eating, Jesus took bread, gave thanks and broke it, and gave it to his disciples, saying, "Take and eat; this is my body." Then he took the cup, gave thanks and offered it to them, saying, "Drink from it, all of you. This is my blood of the covenant, which is poured out for many for the forgiveness of sins.
Mark 14: 24
"This is my blood of the covenant, which is poured out for many," he said to them.
1 Corinthians 11: 24-25, 26-28
and when he had given thanks, he broke it and said, "This is my body, which is for you; do this in remembrance of me." In the same way, after supper he took the cup, saying, "This cup is the new covenant in my blood; do this, whenever you drink it, in remembrance of me." For whenever you eat this bread and drink this cup, you proclaim the Lord's death until he comes. Therefore, whoever eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of sinning against the body and blood of the Lord. A man ought to examine himself before he eats of the bread and drinks of the cup.
1 Corinthians 11: 29
For anyone who eats and drinks without recognizing the body of the Lord eats and drinks judgment on himself.
Touching testimony of a Christian with Alzheimer's remembering how and why she is saved, through the liturgy of holy communion:
Sceleratissimus Lutheranus: Behold, I Am With You Always