Division of the legislative, executive, and judicial functions of government among separate and independent bodies. Such a separation limits the possibility of arbitrary excesses by government, since the sanction of all three branches is required for the making, executing, and administering of laws. The concept received its first modern formulation in the work of Charles-Louis de Secondat, baron de La Brède et de Montesquieu, who declared it the best way to safeguard liberty; he influenced the framers of the Constitution of the United States, who in turn influenced the writers of 19th- and 20th-century constitutions. Seealso checks and balances.
Learn more about separation of powers with a free trial on Britannica.com.