The Anglican Communion is composed of over 70 million members organized into”38 self-governing churches [provinces] made up of about 500 dioceses, 30,000 parishes and 64,000 individual congregations in a total of 164 countries”. These self-governing churches are also referred to as “provinces” of the Anglican Communion.
Colin Buchanan defines a “Province” in the Anglican context as: “A cluster of dioceses, with an organic (usually constitutional) relationship [which] forms a province. The minimum is typically four dioceses to constitute a province, thereby conforming visibly to the requirement that, when there is a vacancy in a bishop’s post, there will still be three bishops available to consecrate a new bishop for the vacancy”. 
Most provinces/churches consist of one country e.g. Church of England, Episcopal Church of Rwanda but some encompass more than one e.g. the Anglican Church of the Southern Cone of America (Argentina, Bolivia, Chile, Paraguay, Peru and Uruguay) and the Church of the Province of West Africa (Cameroon, The Gambia, Ghana, Guinea, Liberia and Sierra Leone).
Internally, most autonomous provinces/churches consist only of dioceses but a few churches are further sub-divided into provinces (sometimes called ecclesiastical provinces) and then into dioceses. Six provinces/churches have an internal provincial structure: the Anglican Church of Australia (5 provinces), the Anglican Church of Canada (4 provinces), the Church of England (2 provinces), the Church of Ireland (2), the Church of Nigeria (10 provinces) and Episcopal Church U.S.A. (9 provinces).
In England and Ireland the archbishops (metropolitans) who head each province are given the title of primate. In all other provinces of the Communion the title of primate is reserved for the head of the national church/province. In Australia, Canada and Nigeria, bishops elected to head a province are referred to as metropolitans or archbishops and addressed as “The Most Reverend”.
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 2007 Church of England Year Book. London: Church House Publishing, 2006. “The Anglican Communion”, p. 337.  Historical Dictionary of Anglicanism / Colin Buchanan. Lanham MD: Scarecrow Pres, 2006. Vide “Province”, p. 373.