an independent state; a republic
(the Commonwealth) a loose association of autonomous states under a common allegiance; specif an association consisting of Britain and states that were formerly British colonies
(the Commonwealth) the British state from 1649 to 1660
a formal title of certain states of the USA
the federal union of Australian states
(the commonwealth) archaic a political unit founded on law and united by agreement of the people for the common good
A commonwealth is defined by Locke (1632–1704) in his second treatise, On Government, as ‘an independent Community’. Today, however, the term means a collection of communities, or rather a community of free and independent states, as opposed to an empire, a form of government in which dependent peoples are ruled by a superior — Professor Vernon Bogdanor
[Middle English commen wealthe, from commen, commun (see common1) + wealthe, welthe welfare: see wealth]