A doctrine is a set of beliefs or principles that a group teaches and follows. When a church has a doctrine, it means it has specific ideas about faith that all members are expected to believe. When a country adopts a military doctrine, it means it has an official strategy for how its armed forces should operate.

Doctrines are teachings that get passed down and treated as important truths. A political party might have doctrines about how government should work. A school of medicine might follow doctrines about how to treat certain diseases.

Doctrines are more formal and fixed than just opinions. If your teacher has a doctrine about homework, she doesn't just casually prefer something: she has a firm principle she believes in and applies consistently. The Monroe Doctrine, announced by President James Monroe in 1823, established America's principle that European powers should not interfere in the Americas.

When someone describes beliefs as doctrinal, they mean these beliefs are official teachings rather than personal views. Doctrines give groups shared principles to unite around.