G2842 Koinōnía Fellowship Partnership

Zodhiates[1]: Participation, communion, fellowship (Acts 2:42; 1 Cor. 1:9; 10:16; 2 Cor. 6:14; 8:4; 13:14; Gal. 2:9.

Kittel[2]: re root koinós:

In Secular Greek. This word means “common” a. in the sense of common ownership, property, ideas, etc., b. in the sense of what concerns all, e.g., societies, monies, resolves, and c. in the sense of what is of little value. 2. A second line of use is for “fellows,” “participants.”
In the New Testament Tit. 1:4 speaks of the “common” faith and Jude 3 of the “common” salvation. In Acts 2:44; 4:32 the disciples live a “common” life, following the example of Jesus (Lk. 8:1ff.) and anticipating the last days (Dt. 15:4). This life in community is not based on economic theory, legal socialization, or philosophical imitation of nature, but expresses the loving fellowship which renounces ownership (cf. Lk. 12:33) in order to help others (Acts 2:45). The phrase in Acts (“having all things or everything in common”) is a Hellenistic one.

[1] Zodhiates, S. (2000). The complete word study dictionary: New Testament (electronic ed.). Chattanooga, TN: AMG Publishers.

[2] Kittel, G., Friedrich, G., & Bromiley, G. W. (1985). Theological Dictionary of the New Testament (p. 447). Grand Rapids, MI: W.B. Eerdmans.