Refers to the political ideology or system advocating a republic, where the head of state is not a monarch. Often used in political or historical contexts.
Republicanism has developed as a political form to replace monarchy.
His paper analyzes the ideas of republicanism during the French Revolution.
共和制 refers specifically to the republican system of government, while 共和制度 is a broader term encompassing the ideology and institutions of republicanism.
君主制 is monarchy, the system opposed to republicanism. 共和制度 is often discussed in contrast to 君主制.
Compound of 共和 (きょうわ, 'republican') + 制度 (せいど, 'system'). 共和 is a Meiji-era coinage from Chinese 共和, originally meaning 'joint harmony' and later used to translate 'republic'.