-ism

-ism repr. F. -isme, L. -ismus — Gr. -ismós, forming nouns of action for vbs. in -īzein -IZE, e.g. baptismós dipping, BAPTISM. A freq. use of -ismós was to express the sense of acting like or adopting the habits of a body of people, as Attikismós siding with Athenians, Attic fashion or idiom; so Ioudaïsmós Judaism, Khristianismós Christianity; on this model was formed medL. pāgānismus PAGANISM. In Eng. Judaism is recorded in XV, and from XVI formations with the suffix become numerous. The chief uses are: (1) to form a noun of action naming the process, the completed action, or its result, e.g. baptism, criticism, nepotism; (2) with emphasis on conduct or character, e.g. barbarism, heroism, patriotism; (3) forming the name of a system of theory or practice, e.g. Arianism, Catholicism, positivism, and (by extension) to designations of doctrines or principles, e.g. agnosticism, altruism, egotism, romanticism, universalism; (4) forming a term denoting a trait or peculiarity, as of language, e.g. Americanism, Gallicism, colloquialism; for (3) and (4) there is an extensive record of nonce-words. Adjectives of sbs. in -ism end in -ISTIC.
Hence ism form of theory, etc., such as may be designated by a word in -ism. XVII.