-ism

Used to form nouns of action, process, or result based on the accompanying verb ending in -ise or -ize.

Used to form the name of a school of thought, system, or theory based on the name of its subject or object or alternatively on the name of its founder (When de-capitalized, these overlap with the generic "doctrines" sense below, e.g. Liberalism vs. liberalism.)

Used to form names of a tendency of action, behaviour, condition, opinion, or state belonging to a class or group of persons, or the result of a doctrine, ideology, or principle or lack thereof.

Used to form countable nouns indicating a peculiarity or characteristic of language

Used to form names of ideologies expressing belief in the superiority of a certain class within the concept expressed by the root word, or a pattern of behavior or a social norm that benefits members of the group indicated by the root word. (Based on a late 20th-century narrowing of the "terms for a doctrine" sense.)

Used to form names of conditions (syndromes, diseases, disorders, defects, addictions) and therapeutical methods or doctrines.