Separation of Powers

• Some modern republics, in one of many borrowings from the government of ancient Greece, divide their administration into more than one branch, separating the executive from the legislative. Governments that do not do this, like that of the modern United Kingdom, draw their executive directly from the legislature, making him accountable to and able to be dismissed by that legislature. Without this check on executive power, separated-power governments must introduce a different set of restrictions.
  
  

Checks and Balances

• The checks and balances of separated-powers governments force each branch of government into reliance on the other branches, making it essentially impossible for any one branch to consistently act without the approval of the others. In this way, even without the direct link between the executive and the legislature, the executive remains accountable to the rest of the government (and vice versa).
  
  

Prevention of Dominance

• The point of the deliberately inefficient checks-and-balances system is the prevention of any single branch of a government from being able to dominate and control the other branches. Preventing any one part of the government from attaining absolute power both ensures government accountability and makes it much more difficult for a single person or political group to take full, unchallenged control of the government.
  
  

The Judiciary

• Systems of government with judicial branches - like the United States' - make every law subject to judicial review. The judicial branch can test a law passed by the legislature and approved by the executive branch against the central laws of the government - in the American case, the Constitution. A law found by the judicial branch to be in violation of these central laws is rendered void.
  
  

List of Checks

• Each power in a separated-power government essentially has a list of specific checks it's granted over each of the other powers - for example, one check belonging to the American legislature is its ability to override a Presidential veto with a sufficient majority, forcing the passage of a law the President has attempted to stop.