"koinwniva" Usage -- A listing of the occurances of the various Greek words which come from the Greek root koin-.
Vine’s Expository Dictionary of Old and New Testament Words

Communion / Fellowship -- The association of believers in the experience of their common salvation, or in the various consequences, expressions, and benefits of salvation.
Bromiley, Geoffrey W., ed, International Standard Bible Encyclopedia

Communion of Saints -- Gr. koinonia, translatable as “communion” or “fellowship,” designates a common sharing or participation in something. It (and its cognate forms) describes the fellowship of true believers with their Lord and with one another.
Pfeiffer, Charles F., Wycliffe Bible Encyclopedia

What is Fellowship? -- Fellowship (Gr. koinoµnia) means companionship or partnership and communion with others on the basis of something held in common. Christian fellowship can be considered under several headings; participants, basis, means of fellowship.
Pfeiffer, Charles F., Wycliffe Bible Encyclopedia

Purpose of the Church -- Two overriding purposes of the church can be delineated: gathered, ministering to the body, and scattered, ministering to the world. It is important to distinguish these two purposes. On the one hand, the church gathers as a body of believers wherein believers minister to one another; on the other hand, the church is to minister the gospel to unbelievers in the world.
Enns, Paul, The Moody Handbook of Theology

Fellowship -- Fellowship, Have, Share, Participate / The following article deals with words which have to do with having, sharing and participation and fellowship. The two key words that are examined together with their associated ideas are echo (have), and koinonia (communion, fellowship).
Dictionary of New Testament Theology