Constitution and Constitutionalism: The Basic Law or set of fundamental rules and principles that govern a polity. In most countries, these rules are recorded in a single written document (the constitution), although basic rules may also reside in accumulated custom, practice, judicial precedents, and ordinary law. A few countries, such as Britain, Israel, and Saudi Arabia do not have written constitutions; instead they rely on convention and precedent to regulate ordinary politics. In these cases, the parliament or monarch is technically sovereign, although ordinarily they are bound by informal rules.