What form of government is best described by the phrase "reigns but does not rule"?

The phrase "reigns but does not rule" aptly characterizes a constitutional monarchy, where a monarch serves as the ceremonial head of state but has limited powers governed by a constitution or laws. In this system, the day-to-day governance is typically carried out by elected officials or a parliament, reflecting democratic principles. The monarch may have some influence and ceremonial responsibilities, yet the true political authority lies elsewhere, often with representatives who are accountable to the populace. This distinguishes a constitutional monarchy from forms of government where rulers possess more absolute power or direct authority.