An "unwritten constitution" refers to a system of governance that is not codified in a single, formal document. Instead, it is based on statutes, legal conventions, judicial decisions, and historical documents. Countries like the United Kingdom exemplify this system, where constitutional principles evolve over time through practice and tradition rather than being explicitly outlined. This type of constitution relies heavily on the interpretation of laws and customs, allowing for flexibility and adaptability. Key elements include parliamentary sovereignty and the rule of law, which guide the functioning of government and protect citizens' rights without a single written framework.