Communion - Vine's Expository Dictionary of New Testament Words
Communion[ A-1,Noun,G2842, koinonia ]
a having in common (koinos), partnership, fellowship" (See COMMUNICATE), denotes
(a) the share which one has in anything, a participation, fellowship recognized and enjoyed; thus it is used of the common experiences and interests of Christian men, Acts 2:42; Galatians 2:9; of participation in the knowledge of the Son of God, 1 Corinthians 1:9; of sharing the realization of the effects of the Blood (i.e., the Death) of Christ and the Body of Christ, as set forth by the emblems in the Lord's Supper, 1 Corinthians 10:16; of participation in what is derived from the Holy Spirit, 2 Corinthians 13:14 (RV, "communion"); Philippians 2:1; of participation in the sufferings of Christ, Philippians 3:10; of sharing in the resurrection life possessed in Christ, and so of fellowship with the Father and the Son, 1 John 1:3, 1 John 1:6-7; negatively, of the impossibility of "communion" between light and darkness, 2 Corinthians 6:14;
(b) fellowship manifested in acts, the practical effects of fellowship with God, wrought by the Holy Spirit in the lives of believers as the outcome of faith, Philemon 1:6, and finding expression in joint ministration to the needy, Romans 15:26; 2 Corinthians 8:4; 2 Corinthians 9:13; Hebrews 13:16, and in the furtherance of the Gospel by gifts, Philippians 1:5. See COMMUNICATION, CONTRIBUTION, DISTRIBUTION, FELLOWSHIP.
[ B-1,Adjective,G2844, koinonos ]
"having in common," is rendered "have communion with (the altar)," --the altar standing by metonymy for that which is associated with it -- in 1 Corinthians 10:18, RV (for AV, "are partakers of"), and in 1 Corinthians 10:20, for AV, "have fellowship with (demons)." See COMPANION.