Heterodox literally means pertaining to "other" doctrines or "other" worship. It is contrasted with "orthodox". In Eastern Orthodoxy, the term is used to refer to Christian churches not belonging to the Eastern Orthodox communion and holding doctrines different from those of Orthodox Christianity, but not as different or as clearly in error as heresy. The word heterodoxy is also used by some other Christians to refer to incorrect religious doctrine.

In a wider sense, heterodox is also used in the sense of any view or school that is not mainstream, such as "heterodox economics" (= non-"standard textbook economics", i.e. formalistic, mathematical-quantitative economics) or "heterodox medicine" (such as TCM).