Prime Minister of Canada
The Prime Minister of Canada is the primary Minister of the Crown, chairman of the Cabinet, and thus head of government of Canada. The office is not outlined in any of the documents that constitute the written portion of the constitution of Canada; executive authority is formally vested in the Canadian sovereign and exercised on his or her behalf by the Governor General. The office was initially modelled after the job as it existed in Britain at time of Confederation in 1867. The British prime ministership, although fully developed by 1867, was not formally integrated into the British constitution until 1905—hence, its absence from Constitution Act, 1867.
The Prime Minister is not elected directly, but is by constitutional convention the leader of the political party that holds the largest number of seats in the House of Commons. According to protocol, all prime ministers are styled Right Honourable (in French: Très Honorable) for life.