2. Ecumenical Denominational Unity (Church Union). This occurs when various denominations merge into one denomination or organized Christian church. The Church of South India is an example of this model. "It came into being by a union of Anglican and Protestant churches in South India. It combined the South India United Church (union of the Congregationalists and the Presbyterians); the then 14 Anglican Dioceses of South India and one in Sri Lanka; and the South Indian District of the Methodist church. With a membership of over four million, it is India's second largest Christian church after the Catholic Church in India." (Wiki)
3. Fellowships, Ecumenical Councils, and Alliances. These are churches and denominations that come together through fellowships, councils, and alliances. Examples are the World Council of Churches, Pentecostal World Fellowship, World Evangelical Alliance, and Global Christian Forum.
4. Ministerial Unity. This is the most significant form of modern Christian unity, in which often the involvement of church leaders, boards, and organizational presence is minimal. This is unity in which individual Christians leap across human-created labels for spiritual profit, for ministerial support, for missions, for worship, for Christian arts, entertainment, and business, and for prayer. It occurs when, for the individual, denominational affiliation of the Christian minister, artist, or business matters less and the ministry and products matter more. Thus, one may buy Christmas cards and Christian movies from stores without inquiring if the business is Catholic, Presbyterian, or Baptist. Here, one may consult commentaries written by Baptists and Anglicans and use quotes from Catholics and stories from the Quakers while preaching to a Charismatic congregation. People of God pray for each other across nations united under the name of only the Lord Jesus Christ. People of God support charity ministries, evangelistic ministries, and teaching ministries with money and goods that they wish to give to the work of God. In this model, being Christian precedes the human labels. In this model, songs written by spiritual men and women of God are sung by believers in all churches through out the world. As they come together, they do not care about the labels.
"There is one body and one Spirit... one Lord, one faith, one baptism; one God and Father of all, who is over all and through all and in all." (Eph.4:4-6)