the.com/separation of powers

means The principle of splitting government into independent legislative, executive, and judicial branches so no single branch can seize total control.

from The core idea traces back to Aristotle's observation that governments have deliberative, official, and judicial functions, but the modern phrase owes its shape to the 18th-century French thinker Montesquieu, who in 'The Spirit of the Laws' argued liberty depended on keeping these powers in separate hands — drawing partly on (an idealized reading of) the English constitution. His framework went on to directly inform the architects of the U.S. Constitution, who built it into the system of checks and balances.