A Member of Parliament (MP) is the representative of the voters to a parliament. In many countries with bicameral parliaments, this category includes specifically members of the lower house, as upper houses often have a different title. Member of Congress (MOC) is an equivalent term in other jurisdictions.
Members of parliament tend to form parliamentary groups (also called parliamentary parties) with members of the same political party.
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.
A member of parliament is a member of the House of Representatives, the lower house of the Commonwealth (federal) parliament. Members may use "MP" after their names; "MHR" is not used, although it was used as a post-nominal in the past. A member of the upper house of the Commonwealth parliament, the Senate, is known as a "Senator".
In the Australian states of New South Wales, Victoria and South Australia, a Member of the Legislative Assembly (House of Assembly in South Australia) or "lower house," may also use the post-nominal "MP." Members of the Legislative Council (upper house) use the post-nominal "MLC."