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A person entitled to sit and vote in Parliament. The term is not usually taken to refer to the House of lords, although that House is technically part of Parliament as well as the house of commons. There are about 600 seats in the House of Commons, hence 600 MPs must be elected. MPs are elected by a simple majority system, and serve for a four year term. There are no (legal) limits on the number of terms which may be served; the only limits are the health and enthusiasm of the MP and, of course, the tolerance of the electorate.