A rigid constitution has a formal and often difficult process of amendment. This means that significant changes to the constitution need direct approval from the electorate or a supermajority in the legislative body. This makes it more challenging to amend compared to flexible constitutions.

In contrast, a flexible constitution can be amended more easily, often through ordinary legislative processes without the need for special procedures like a plebiscite or referendum. A written constitution is codified in a single document, while an unwritten constitution consists of statutes, legal conventions and judicial decisions.