Data source: Gina A. Zurlo and Todd M. Johnson, eds., World Christian Database (Leiden/Boston: Brill, 2024).
| Glossary item | Definition |
|---|---|
| unchurched | Christians unaffiliated to organized churches, not belonging to or connected with a church; nominal Christians (qv). |
| under discipline | See discipline. |
| under obligation | All baptized Catholics of 7 years and older are obligated by canon law to attend Easter mass once a year. |
| underground churches, underground Christians | See crypto-Christians. |
| underground communities | See basic communities. |
| unevangelized | The state of not having had the gospel spread or offered. |
| unevangelized | Never having heard the Good News of Jesus Christ. |
| unevangelized persons | Individuals who have had no adequate opportunity to hear the gospel or respond to it; persons who are unaware of Christianity, Christ, and the gospel; those who have never heard the name of Jesus. |
| unevangelized World | In the 3-tier schema, this is World A, consisting of all non-Christians who have not been evangelized. |
| unfinished task | The remaining task of evangelization, as the task of the Christian church on Earth, viewed as the church’s responsibility usually viewed as completing the fulfillment of Christ’s Great Commission, |
| Uniate | Christian or a jurisdiction of an Eastern rite not belonging to a Latin patriarchate but in union with and submitting to the authority of the Roman papacy. |
| unimax people | An alternate term for minipeople emphasizing the maximum size of people in which the gospel can spread before encountering barriers. |
| union congregations | Churches of English-speaking peoples abroad in which several denominations are present and hence an interdenominational ministry is required. |
| Union of Utrecht | International Old Catholic Bishops Conference (qv). |
| union, church | See church unions. |
| Unitarian-Pentecostals | Oneness-Pentecostals (qv). |
| Unitarians | Non-Trinitarians (denying the Trinity), Universalists, Free Christians, Liberal Christians: a marginal Protestant tradition in the direction of modernism. |
| united churches | Protestant and Anglican denominations which in recent years have united to form new united denominations. |
| united diocese, united dioceses | Dioceses which were large in the past but have now shrunk numerically (especially in Ireland), so are administered together as a single diocese. |
| united seminary | A theological college serving 2 or more denominations or confessions. |
| uniting churches | Churches or denominations that are in process of merging to form a united church. |
| unity | Oneness, singleness, accord among Christians of different traditions. |
| Unity of the Brethren | Moravians (qv). |
| unity undertaking | A Moravian jurisdiction. |
| universal church | The Christian church in its world-wide entirety down the ages; in Catholic usage, the worldwide church as contrasted with local or particular churches (qv). |
Data on 18 categories of religion, including non-religious, by country, province, and people.
Data on all religions, Christian activities, and trends.
Membership data, year begun, and rates of change.
Population and religion data on all major cities & provinces.
Detailed information covering religion, culture, and geography.
A repository of historical data, including a chronology of Christianity from the 1st to 21st centuries.