advocate; ideologist; ideologue
Refers to a person who actively supports or promotes a particular theory, principle, or ideology. Often used in formal or intellectual contexts.
彼は自由主義の主義者として知られている。
He is known as an advocate of liberalism.
He calls himself a pacifist, but his actions are contradictory.
-ist (adherent)
Suffix attached to nouns denoting a belief system or principle to form a word for a follower or adherent. Very productive; e.g., 平和主義者 (pacifist), 菜食主義者 (vegetarian).
彼女は菜食主義者で、肉を一切食べない。
She is a vegetarian and doesn't eat any meat.
socialist; communist; anarchist
Archaic use specifically referring to left-wing political adherents, especially socialists, communists, or anarchists. Now largely replaced by more specific terms like 社会主義者 or 共産主義者.
明治時代には、主義者という言葉が社会主義者を指すことがあった。
In the Meiji period, the word 主義者 sometimes referred to socialists.
She is a devoted environmentalist.
He calls himself a democrat, but in reality he's authoritarian.
主義者 specifically denotes an adherent of a named -ism (often formed by attaching 主義者 to a doctrine word), while 信奉者 more broadly means a devoted believer or follower of any idea, person, or religion.
支持者 means a supporter who backs a person, policy, or cause, whereas 主義者 implies deeper ideological commitment to a system of belief.
主義者 is someone who advocates for a doctrine, while 反対者 is someone who opposes it.
主義 is the principle or doctrine itself, while 主義者 (with the added 者) refers to the person who holds that principle.
The everyday counter for people: 一人 (ひとり), 二人 (ふたり), 三人 (さんにん).
名 is used instead of 人 in more formal or written contexts when counting 主義者.
voluntarist
egoist
intellectualist
subjectivist
humanitarian
Compound of 主義 (principle, doctrine) + 者 (person). The suffix usage is a direct calque from Western '-ist' formations.
totalitarian
communist