Concept
A member of parliament (MP) is the representative in parliament of the people who live in their electoral district. In many countries with bicameral parliaments, this term refers only to members of the lower house since upper house members often have a different title. The terms congressman/congresswoman or deputy are equivalent terms used in other jurisdictions. The term parliamentarian is also sometimes used for members of parliament, but this may also be used to refer to unelected government officials with specific roles in a parliament and other expert advisers on parliamentary procedure such as the Senate parliamentarian in the United States. The term is also used to the characteristic of performing the duties of a member of a legislature, for example: "The two party leaders often disagreed on issues, but both were excellent parliamentarians and cooperated to get many good things done." Members of parliament typically form parliamentary groups, sometimes called caucuses, with members of the same political party. Westminster system The Westminster system is a democratic parliamentary system of government modelled after the politics of the United Kingdom. This term comes from the Palace of Westminster, the seat of the Parliament of the United Kingdom. At the Commonwealth level, a "member of parliament" is a member of the House of Representatives, the lower house of the Commonwealth (federal) parliament. Members may use the postnominal "MP" after their names. "MHR" ("Member of the House of Representatives") was not used, which was affirmed by cabinet in 1901 and reaffirmed in 1951 and 1965. However, the prohibition of "MHR" does not appear to have been strictly enforced, as it was used most recently by Tony Abbott when he was in the parliament (1994–2019). A member of the upper house of the Commonwealth Parliament, the Senate, is known as a "Senator". In the Australian states and territories, "MP" is commonly used.