noun
extremism; radicalism
Refers to political or ideological extremism; often used in news and formal contexts.
過激主義の台頭が懸念されている。
The rise of extremism is a concern.
彼は過激主義に染まってしまった。
He fell into radicalism.
過激派 refers to a radical faction or group, while 過激主義 is the ideology of extremism itself.
Compound of 過激 (kageki, 'extreme') and 主義 (shugi, 'ism'). The exact historical derivation is uncertain, but the word follows standard Sino-Japanese word formation patterns.