A "republic" is a form of government in which the country is considered a "public matter," and is not the private concern or property of the rulers. In a republic, the affairs of the state are a public matter, and thus officials are accountable to the public and must govern according to existing constitutional law that limits the government's power over citizens.
The word "republic" comes from the Latin phrase "res publica," which means "public matter." It is derived from "res," meaning "thing" or "matter," and "publicus," meaning "of the people."