Fellowship with God (Genesis 18:17-33; Exodus 33:9-11; Numbers 12:7,8), between Christ and his people (John 14:23), by the Spirit (2 Corinthians 13:14; Phil 2:1), of believers with one another (Ephesians 4:1-6). The Lord's Supper is so called (1 Corinthians 10:16,17), because in it there is fellowship between Christ and his disciples, and of the disciples with one another.
These dictionary topics are from M.G. Easton M.A., D.D., Illustrated Bible Dictionary, Third Edition, published by Thomas Nelson, 1897. Public Domain, copy freely.
Easton, Matthew George. "Entry for 'Communion'". "Easton's Bible Dictionary".