The House of Commons is the lower house of the Parliament of the United Kingdom, which also comprises the Sovereign and the House of Lords (the upper house). Both Commons and Lords meet in the Palace of Westminster. The Commons is a democratically elected body, consisting of 646 members, who are known as "Members of Parliament" or MPs. Members are elected, through the first-past-the-post system, by electoral districts known as constituencies, and hold their seats until Parliament is dissolved (a maximum of five years).
The House of Commons evolved at some point during the 14th century and has been in continuous existence since. The House of Commons was originally far less powerful than the House of Lords, but today its legislative powers exceed those of the Lords. Under the Parliament Act 1911, the Lords' power to reject most legislative bills was reduced to a delaying power. Moreover, the Government is primarily responsible to the House of Commons; the Prime Minister stays in office only as long as he or she retains its support. The full, formal style and title of the House of Commons is The Honourable the Commons of the United Kingdom of Great Britain and Northern Ireland in Parliament assembled.