Commonwealth is a term used to describe a state where the supreme power is vested in the people.
The Commonwealth of England was the term used to describe the republican state created by the Cromwellians from 1649 until the restoration of the British monarchy in 1660.
The title Commonwealth occurs in the formal names of several US states, such as Virginia, Massachusetts and Pennsylvania, and is similarly used by the US territory of Puerto Rico.
Commonwealth also appears in the name Commonwealth of Australia. In every day use the Australian federal government and its agencies are referred to as the Commonwealth.
The most common modern reference to commonwealth refers to the Commonwealth of Nations, an organisation whose members were, with a few exceptions, formerly part of the British Empire.