commonwealth (plural commonwealths)
- A form of government, named for the concept that everything that is not owned by specific individuals or groups is owned collectively by everyone in the governmental unit, as opposed to a state, where the state itself owns such things.
- Approximately, a republic.
- May 19, 1649 Be it declared and enacted by this present Parliament and by the Authoritie of the same That the People of England and of all the Dominions and Territoryes thereunto belonging are and shall be and are hereby constituted, made, established, and confirmed to be a Commonwealth and free State And shall from henceforth be Governed as a Commonwealth and Free State by the supreame Authoritie of this Nation, the Representatives of the People in Parliam[ent] and by such as they shall appoint and constitute as Officers and Ministers under them for the good of the People and that without any King or House of Lords. Act of the Long Parliament.
Derived terms 
For example, the official name of Australia is Commonwealth of Australia. It is applied to four states of the United States, to wit, the Commonwealth of Pennsylvania, the Commonwealth of Kentucky, the Commonwealth of Massachusetts, and the Commonwealth of Virginia. Also used by self-governing, semi-autonomous units such as the Commonwealth of Puerto Rico.