A constitution is a set of fundamental principles, norms, and laws that govern a political or other organization. The term can refer either to a body of rules and practices that establish the elements of government and allocate government power, or to a foundational written document designed to do the same. Modern national written constitutions generally contain several key elements, including a bill of rights, a division of powers between government entities, and a claim to supremacy over other sources of internal law. The primary functions of constitutions may include intra-government coordination, rule precommitment, solidifying power, articulating national identity, and signaling to international audiences. 

Kevin Cope & Mila Versteeg, Constitutions, in International Encyclopedia of the Social & Behavioral Sciences, Elsevier, 710–715 (2 ed. 2015).