A constitution is a set of fundamental principles or established precedents according to which a state or other organization is governed. These rules together make up, i.e. constitute, what the entity is.

A treaty which establishes an international organization is also its constitution, in that it would define how that organization is constituted. Within states (not the United States), a constitution defines the principles upon which the state is based, the procedure in which laws are made and by whom. Some constitutions, especially codified constitutions, also act as limiters of state power, by establishing lines which a state's rulers cannot cross, such as fundamental rights.<p>

The Constitution of India is the longest written constitution of any sovereign country in the world, while the Constitution of Monaco is the shortest written constitution.

- extracted from Constittuion, Wikipedia as on 7th January, 2018

It should be noted that it is possible to make Ammendmends to the Constitution.