A seminary, school of theology, theological seminary, or divinity school is an educational institution for educating students (sometimes called seminarians) in scripture, theology, generally to prepare them for ordination to serve as clergy, in academics, or mostly in Christian ministry.  The English word is taken from the Latin seminarium, translated as seed-bed, an image taken from the Council of Trent document Cum adolescentium aetas which called for the first modern seminaries. 
In the United States, the term is currently used for graduate-level theological institutions, but historically it was used for high schools.
The establishment of modern seminaries resulted from Roman Catholic reforms of the Counter-Reformation after the Council of Trent.  The Tridentine seminaries placed great emphasis on personal discipline as well as the teaching of philosophy as a preparation for theology.  In the United States, Protestant institutions widely adopted the term 'seminary' for independent graduate schools (separate from a university) to train its ministers. The oldest seminary in the United States was Andover Theological Seminary founded in 1807 and affiliated with the Congregationalist Church.
Seminaries in the Catholic Church are divided into minor seminaries for teenagers and major seminaries for adults, including both college seminaries (though in the U.S. these are often called minor seminaries) for undergraduate students and post-graduate seminaries for those who already have a bachelor's degree. There are also seminaries for older adults who are well out of school, such as the Pope St. John XXIII National Seminary in Massachusetts, and for other more specialized purposes.
All seminaries are run either by religious orders or by dioceses or other similar structures. Often a seminary will train both that particular order's or diocese's priests and the priests of other orders or dioceses that select that particular seminary for its priests. For instance, Saint John's Seminary in Boston, Massachusetts trains priests for many of the other dioceses in New England which are suffragan dioceses of the Roman Catholic Archdiocese of Boston. Either way, a man who seeks to enter a seminary to become a priest must be sponsored by either a diocese or by a religious order.
Often a diocese might be attached to or affiliated with a larger Catholic college or university so that the larger college and its faculty provides more general education in history or theology while the seminary focuses on topics specific to the needs of future priests, such as training in canon law, the sacraments, and preaching, or specific to the particular order or diocese. For instance the Theological College in Washington, D.C. is part of The Catholic University of America.
Further, in Rome there are several seminaries which educate seminarians or already ordained priests and bishops and which are maintained by orders or dioceses from outside of Italy. For instance, the Pontifical North American College, which trains priests from the United States and elsewhere, is supported by the United States Conference of Catholic Bishops.
The International Council for Evangelical Theological Education was founded in 1980 by the Theological Commission of the World Evangelical Alliance.  In 2015, it would have 1,000 member schools in 113 countries. 
In some countries, the term seminary is also used for secular schools of higher education that train teachers; in the nineteenth century, many female seminaries were established in the United States. 
The Church of Jesus Christ of Latter-day Saints (LDS Church) hosts seminary classes for high school students ages 14 to 18, as part of the Church Educational System. Unlike use in other religious contexts, the word "seminary", in an LDS Church context, does not refer to a higher education program designed to train students that they may obtain a church-based career.  LDS seminary students do not get high school credit for their seminary studies.
- Consecrated life
- Bible college
- List of Eastern Catholic seminaries
- List of evangelical seminaries and theological colleges
- List of Roman Catholic seminaries
- Minor seminary
- Female seminary
- Jewish use: Yeshiva, and especially Midrasha, the women's equivalent, widely referred to as "seminaries"
- Madrasa in Islam
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- XXIII Session, Council of Trent, ch. XVIII. Retrieved from J. Waterworth, ed. (1848). The Canons and Decrees of the Sacred and Oecumenical Council of Trent. London: Dolman. pp. 170–92. Archived from the original on June 10, 2009. Retrieved June 16, 2009.
- Glazier, Michael; Hellwig, Monika, eds. (2004). "Ecumenical Councils to Trent". The Modern Catholic Encyclopedia. Collegeville, Michigan: Liturgical Press. p. 263. ISBN 978-0-8146-5962-5.
- Rose, Michael S. (2002). Goodbye, Good Men. Regnery Publishing. pp. 217–25. ISBN 0-89526-144-8.
- Bernhard Ott, Understanding and Developing Theological Education, Langham Global Library, UK, 2016, p. 23
- Brian Stiller, Evangelicals Around the World: A Global Handbook for the 21st Century, Thomas Nelson, USA, 2015, p. 170
- "The Rise of Women's Colleges, Coeducation". The Women's College Coalition. Archived from the original on September 3, 2011. Retrieved June 24, 2011.
- Mauss, Armand L. (2003). All Abraham's Children. University of Illinois Press. pp. 84–85. ISBN 978-0-252-02803-8. Archived from the original on 2016-10-22. Retrieved 2008-09-12.