There are several types of constitutions that govern countries around the world. A written constitution is a formal document that outlines the fundamental laws and principles of a nation, such as the United States Constitution. In contrast, an unwritten constitution is based on customs, conventions, and legal precedents, as seen in the United Kingdom. Another classification is the rigid constitution, which requires a special procedure for amendments, making it difficult to change. Conversely, a flexible constitution can be amended through the same process as ordinary laws, allowing for easier adjustments to the legal framework, as seen in many parliamentary systems.