It is often said that the US has a written constitution, while the British constitution is unwritten. In reality, it means that the US has a formal document called the "Constitution", but Great Britain has no such document. Yet, all parts of the British constitution exist in written form. They are set out in different documents. The most important historical documents are the Magna Carta, the Petition of Rights, the Habeas Corpus Act, the Bill of Rights, and the Act of Settlement. The American constitution is short, but many of its important aspects are unwritten.
In fact, the American constitution is the shortest. It contains about 7,000 words. The constitutions of Western countries are a little longer, while the constitution of India contains hundreds of pages.
The British constitution is flexible. It can be changed, amended or abolished just like any other law.
The United States has a rigid constitution. Amendments to the Constitution are a complex procedure that requires a majority vote in each house of Congress.
The constitutions of Great Britain and the US are normative constitutions. Their principles are observed in life. If the principles set out in constitutions are not observed in real life, such constitutions are called "nominal" constitutions. Nominal constitutions exist on paper only because their principles are disregarded by the real functioning of the system. Such constitutions are characteristic of developing countries and authoritarian regimes.