Doctrine (from Latin: doctrina, meaning "teaching", "instruction" or "doctrine") is a codification of beliefs or a body of teachings or instructions, taught principles or positions, as the essence of teachings in a given branch of knowledge or in a belief system. The etymological Greek analogue is "catechism".
Often the word doctrine specifically suggests a body of religious principles as promulgated by a church. Doctrine may also refer to a principle of law, in the common-law traditions, established through a history of past decisions, such as the doctrine of self-defense, or the principle of fair use, or the more narrowly applicable first-sale doctrine. Some organizations simply define doctrine as "that which is taught", or the basis for institutional teaching to its personnel of internal ways of operating.
Examples of religious doctrines include:
- Christian theology:
- Doctrines such as the Trinity, the virgin birth and atonement
- The Salvation Army Handbook of Doctrine, available in print  and online 
- Transubstantiation and Marian teachings in Roman Catholic theology. The department of the Roman Curia which dea;s with questions of doctrine is called the Congregation for the Doctrine of the Faith.
- The distinctive Calvinist doctrine of "double" predestination
- The Methodist Church of Great Britain refers to the "doctrines to which the preachers of the Methodist Church are pledged" as doctrinal standards 
- Yuga in Hinduism
- Postulation or Syādvāda in Jainism
- The Four Noble Truths in Buddhism
As a measure of religiosity in the sociology of religion
The content of a doctrine may vary from one religion to the next, as will the degree to which it may occupy the person's mind (frequency), the intensity of the doctrine, and the centrality of the doctrine (in that religious tradition).
The term also applies to the concept of an established procedure to a complex operation in warfare. The typical example is tactical doctrine in which a standard set of maneuvers, kinds of troops and weapons are employed as a default approach to a kind of attack.
Examples of military doctrines include:
- Guerre de course
- Hit-and-run tactics
- Mahanian of late 19th up to mid-20th century
- Manhunting doctrine, or assured individual destruction
- Reagan Doctrine of the Cold War
- Shock and Awe
- Soviet deep battle of World War II
- Trench warfare of World War I
Almost every military organization has its own doctrine, sometimes written, sometimes unwritten. Some military doctrines are transmitted through training programs. More recently, in modern peacekeeping operations, which involve both civilian and military operations, more comprehensive (not just military) doctrines are now emerging such as the 2008 United Nations peacekeeping operations' "Capstone Doctrine" which speaks to integrated civilian and military operations.
By definition, political doctrine is "[a] policy, position or principle advocated, taught or put into effect concerning the acquisition and exercise of the power to govern or administrate in society." The term political doctrine is sometimes wrongly identified with political ideology. However, doctrine lacks the actional aspect of ideology. It is mainly a theoretical discourse, which "refers to a coherent sum of assertions regarding what a particular topic should be" (Bernard Crick). Political doctrine is based on a rationally elaborated set of values, which may precede the formation of a political identity per se. It is concerned with philosophical orientations on a meta-theoretical level.
A legal doctrine is a body of inter-related rules (usually of common law and built over a long period of time) associated with a legal concept or principle. For example, the doctrine of frustration of purpose now has many tests and rules applicable with regards to each other and can be contained within a "bubble" of frustration. In a court session a defendant may refer to the doctrine of justification.
It can be seen that a branch of law contains various doctrines, which in turn contain various rules or tests. The test of non-occurrence of crucial event is part of the doctrine of frustration which is part of contract law. Doctrines can grow into a branch of law; restitution is now considered a branch of law separate to contract and tort.
- Betancourt Doctrine
- Bush Doctrine
- Carter Doctrine
- Drago Doctrine
- Giedroyc Doctrine
- Hallstein Doctrine
- Monroe Doctrine
- Truman Doctrine
- Doctrine – Definition at WordIQ.com 2010
- Handbook of Doctrine. Salvation Books. ISBN 978-0-85412-822-8.
- "Handbook of Doctrine website page".
- "Congregation for the Doctrine of the Faith (Roman Catholic Church) – Britannica Online Encyclopedia". Britannica.com. Retrieved 2013-03-07.
- "Congregation for the Doctrine of the Faith". Ewtn.com. Retrieved 2013-03-07.
- Doctrine of the Methodist Church, accessed 25 may 2018
- Verbit, M. F. (1970). The components and dimensions of religious behavior: Toward a reconceptualization of religiosity. American mosaic, 24, 39.
- Küçükcan, T. (2010). Multidimensional Approach to Religion: a way of looking at religious phenomena. Journal for the Study of Religions and Ideologies, 4(10), 60–70.
- "Microsoft Word - M-26.doc" (PDF). Retrieved 2018-09-24.
- Glock, C. Y. (1972) ‘On the Study of Religious Commitment’ in J. E. Faulkner (ed.) Religion’s Influence in Contemporary Society, Readings in the Sociology of Religion, Ohio: Charles E. Merril: 38–56.
- "Peacekeeping Resource Hub" (PDF). pbpu.unlb.org. Retrieved 27 March 2018.
- "Political doctrine (definition)". Eionet.europa.eu. 2012-07-20. Retrieved 2013-03-07.
- Dr. Daniel Șandru. "Ideology, Between the Concept and the Political Reality". The Knowledge Based Society Project. Sfera Politicii nr. 169. Retrieved March 10, 2013.