A distinction must be made between a British "dominion" and British "Dominions". The use of a capital "D" when referring to the 'British Dominions' was required by the United Kingdom government in order to avoid confusion with the wider term "His Majesty's dominions" which referred to the British Empire as a whole.
All territories forming part of the British Empire were British dominions but only some were British Dominions. At the time of the adoption of the Statute of Westminster, there were six British Dominions: Canada, Australia, New Zealand, South Africa, Newfoundland, and the Irish Free State. At the same time there were many other jurisdictions that were British dominions, for example Cyprus. The Order in Council annexing the island of Cyprus in 1914 declared that, from 5 November, the island "shall be annexed to and form part of His Majesty's dominions".
Use of dominion to refer to a particular territory dates back to the 16th century and was sometimes used to describe Wales from 1535 to around 1800: for instance, the Laws in Wales Act 1535 applies to "the Dominion, Principality and Country of Wales". Dominion, as an official title, was conferred on the Colony of Virginia about 1660 and on the Dominion of New England in 1686. These dominions never had full self-governing status. The creation of the short-lived Dominion of New England was designed—contrary to the purpose of later dominions—to increase royal control and to reduce the colony's self-government.
Under the British North America Act 1867, what is now eastern Canada received the status of "Dominion" upon the Confederation of several British possessions in North America. However, it was at the Colonial Conference of 1907 when the self-governing colonies of Canada and the Commonwealth of Australia were referred to collectively as Dominions for the first time. Two other self-governing colonies—New Zealand and Newfoundland—were granted the status of Dominion in the same year. These were followed by the Union of South Africa in 1910 and the Irish Free State in 1922. At the time of the founding of the League of Nations in 1924, the League Covenant made provision for the admission of any "fully self-governing state, Dominion, or Colony", the implication being that "Dominion status was something between that of a colony and a state".