communicate (have fellowship) with, be partaker of

Concise Bible Dictionary:

This in scripture is association, and having things in common. The Lord's table is where the fellowship of Christians is expressed—all there being associated in the fellowship of Christ's death. Being thus associated, proper christian fellowship is in the light of God fully revealed—the Father and the Son. The apostles specially made known the truth of this fellowship as specially given to know it (1 John 1:33That which we have seen and heard declare we unto you, that ye also may have fellowship with us: and truly our fellowship is with the Father, and with his Son Jesus Christ. (1 John 1:3)). Being brought into such association, it follows that as regards the gospel for the world, the welfare of the saints, and the maintenance of the truth, the believer has the same aims and objects before his soul as the Father and the Lord Jesus Christ have. Out of this flows the fellowship of the saints one with another (Acts 2:4242And they continued stedfastly in the apostles' doctrine and fellowship, and in breaking of bread, and in prayers. (Acts 2:42); 2 Cor. 8:44Praying us with much entreaty that we would receive the gift, and take upon us the fellowship of the ministering to the saints. (2 Corinthians 8:4); Gal. 2:99And when James, Cephas, and John, who seemed to be pillars, perceived the grace that was given unto me, they gave to me and Barnabas the right hands of fellowship; that we should go unto the heathen, and they unto the circumcision. (Galatians 2:9); 1 John 1:3-73That which we have seen and heard declare we unto you, that ye also may have fellowship with us: and truly our fellowship is with the Father, and with his Son Jesus Christ. 4And these things write we unto you, that your joy may be full. 5This then is the message which we have heard of him, and declare unto you, that God is light, and in him is no darkness at all. 6If we say that we have fellowship with him, and walk in darkness, we lie, and do not the truth: 7But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin. (1 John 1:3‑7)). It is also called the fellowship of the Spirit (2 Cor. 13:1414The grace of the Lord Jesus Christ, and the love of God, and the communion of the Holy Ghost, be with you all. Amen. <<The second epistle to the Corinthians was written from Philippi, a city of Macedonia, by Titus and Lucas.>> (2 Corinthians 13:14); Phil. 2:11If there be therefore any consolation in Christ, if any comfort of love, if any fellowship of the Spirit, if any bowels and mercies, (Philippians 2:1)). The converse of this is also true: Christians cannot consistently have any fellowship with that which is evil or which brings dishonor upon the Lord Jesus (Psa. 94:2020Shall the throne of iniquity have fellowship with thee, which frameth mischief by a law? (Psalm 94:20); 1 Cor. 10:2020But I say, that the things which the Gentiles sacrifice, they sacrifice to devils, and not to God: and I would not that ye should have fellowship with devils. (1 Corinthians 10:20); 2 Cor. 6:1414Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness? (2 Corinthians 6:14); Eph. 5:1111And have no fellowship with the unfruitful works of darkness, but rather reprove them. (Ephesians 5:11)).
In some passages the A. V. has the word “COMMUNION” for the same Greek word, with the same meaning. Thus in 1 Corinthians 10:1616The cup of blessing which we bless, is it not the communion of the blood of Christ? The bread which we break, is it not the communion of the body of Christ? (1 Corinthians 10:16), "The cup of blessing which we bless, is it not the communion of the blood of Christ? The bread which we break, is it not the communion of the body of Christ?" There is an allusion to the peace offering in verse 18 to show that those who ate the sacrifice were partakers of, had communion with, the altar; hence to eat things offered to idols would be to have fellowship with demons.

Strong’s Dictionary of Greek Words:

Number:
4790 (find all occurrences in KJV Bible)
Greek:
συγκοινωνέω
Transliteration:
sugkoinoneo
Phonic:
soong-koy-no-neh’-o
Meaning:
from 4862 and 2841; to share in company with, i.e. co-participate in
KJV Usage:
communicate (have fellowship) with, be partaker of