As a common noun, Commonwealth means 'the general good', 'public welfare', or, more specifically, 'a Republic'. The word was originally interchangeable with the two words common weal (= 'the general well-being'), but this phrase is now only archaic.
As a proper noun, Commonwealth has several different meanings.
- In British history, it refers to the Republic established after the execution of Charles I in 1649, which ended (as a Protectorate) with the Restoration in 1660.
- In current international politics, the Commonwealth in the UK is the usual way to refer to what is more formally known as the Commonwealth of Nations, formerly the British Commonwealth of Nations: the association of those countries that were formerly part of the British Empire, many of which still have Elizabeth II as Head of State. A similar loose grouping known as the Commonwealth of Independent States, or CIS, as a successor umbrella to the now independent countries, was formed in 1991 on the break-up of the Soviet Union.
- In various constitutions, some countries are known as Commonwealths: for example, the states of Kentucky, Massachusetts, Pennsylvania, and Virginia in the USA are formally known as Commonwealths, and the federation of states usually called 'Australia' is officially The Commonwealth of Australia.