The Greek verb koinoneo means to share, participate in, or have fellowship with. It is the verbal form of koinonia (G2842), fellowship/communion. The word denotes active participation and sharing — not merely proximity but genuine mutual involvement in something common.
Koinoneo and its cognates describe the revolutionary community life that the gospel creates. To koinoneo is to enter genuine partnership — sharing material goods (Romans 12:13), participating in Christ's sufferings (Philippians 3:10), and experiencing the communion of the Holy Spirit (2 Corinthians 13:14). Paul uses the word for financial support of ministry — the Philippians 'shared' in his troubles (Philippians 4:15). The dark side appears in warnings not to koinoneo in the sins of others (1 Timothy 5:22) or in unfruitful works of darkness (Ephesians 5:11). True Christian community requires both generous sharing and careful boundary-keeping against what corrupts.