Separation of powers is one of the primary safeguards of democratic systems of government. Powers are apportioned to specific areas of law and government, acting as checks on each other. The legislature passes laws, the judicial system tests those laws. The concept of separation of powers is an old one, dating back to ancient Greece. The Roman Republic produced the most effective ancient form of separation of powers, with a three tier system of the Senate, Assemblies, and Magistrate filling the basic roles of law makers, administrative government and judiciary. The US constitution has a similar basic structure with the addition of the Presidential office.
Examples of Separation of Powers:
The United states capitol dome as seen from the supreme court building.