Types of constitution

A constitution is the body of rules, written or unwritten, by which a state is governed. It sets out the structure of government and the rights and duties of citizens.

A written constitution is contained in a single document, like Nigeria's 1999 Constitution. An unwritten constitution, as in Britain, is drawn from conventions, statutes and judicial decisions.

A rigid constitution is difficult to amend and usually requires a special majority or referendum, while a flexible one can be changed by an ordinary act of parliament. Nigeria's constitution is written and rigid.