militia

Latin militia meant 'military service' or 'warfare,' from miles, 'soldier.' In Roman usage, it was abstract — the condition of being a soldier, the practice of war. It did not refer to a specific group of armed civilians. A Roman miles served in the legions. His militia was his service.

The meaning shifted in medieval Europe. As feudal states lacked standing armies, local defense fell to armed citizens who could be called up in emergencies. These citizen-soldiers were distinguished from professional armies and mercenaries. English adopted militia in the 1580s for exactly this concept — an organized force of non-professional citizens bearing arms in defense of their community.

The Second Amendment to the U.S. Constitution (ratified 1791) begins: 'A well regulated Militia, being necessary to the security of a free State.' The founders were thinking of citizen-soldiers on the model of the Minutemen — farmers who grabbed muskets and assembled. Whether 'militia' referred to all citizens or only organized groups became one of the most contested questions in American constitutional law, culminating in District of Columbia v. Heller (2008).

Outside the United States, militia often describes irregular armed groups — paramilitary organizations, rebel forces, tribal warriors. The Janjaweed in Sudan, the Interahamwe in Rwanda, the various militias of the Lebanese Civil War. The Latin word for 'military service' now names everything from constitutional self-defense to war crimes. Context determines which militia you mean.