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early 15c., from Old French dominion "dominion, rule, power," from Medieval Latin dominionem (nominative dominio), corresponding to Latin dominium "property, ownership," from dominus (see domination).
British sovereign colonies often were called dominions, hence the Dominion of Canada, the formal title after the 1867 union, and Old Dominion, the popular name for the U.S. state of Virginia, first recorded 1778.
the status, prior to 1939, of each of the British Commonwealth countries of Canada, Australia, New Zealand, the Union of South Africa, Eire, and Newfoundland. Although there was no formal definition of dominion status, a pronouncement by the Imperial Conference of 1926 described Great Britain and the dominions as "autonomous communities within the British Empire, equal in status, in no way subordinate one to another in any aspect of their domestic or external affairs, though united by a common allegiance to the Crown and freely associated as members of the British Commonwealth of Nations."