The United Kingdom, Isreal, New Zealand, and Saudi Arabia are among countries that have uncodified constitutions, which means the laws are written in these countries, but an overriding document does not necessarily define them.
For example, the UK's legal system is run by Parliament. The United Kingdom's laws are passed by Parliament and are called statutes. Statutes are codified as the highest form of law in the country. Connections are unwritten practices that develop over time and offer guidelines. Some guidelines govern Great Britain. The uncoded constitution is sometimes written as “unwritten constitution,” although its elements are written down in several official documents. Under the uncodified constitution, new conditions and situations of government are resolved by precedent or passing legislation.
No, not all countries in the world have constitutions. Some countries like the United States and Australia have written constitutions. Other countries like Israel and the United Kingdom have constitution-like documents. A very interesting article published by Tom Ginsberg called, “Written Constitutions Around the World”, says, “Including now-defunct countries such as the Central American Republic and the Ottoman Empire, there have been more than 220 different nation-states in existence since 1789.
These countries have produced more than 900 constitutions in that time span.” Why so many more constitutions than countries? Some countries change their constitutions numerous times. For example, Haiti has had 24-25 constitutions in the last 200 years, 5 of them in the last 50 years.