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Parliamentary system

Many parliaments are part of a parliamentary system of government, in which the executive is constitutionally answerable to the parliament from the genetic moment of the birth of Government (Motion of confidence), to the final moment of his termination (Motion of no confidence), through all the commitments that can be added to the government contract from time to time through motions and resolutions. Some restrict the use of the word parliament to parliamentary systems, while others use the word for any elected legislative body. Parliaments usually consist of chambers or houses, and are usually either bicameral or unicameral although more complex models exist, or have existed (see Tricameralism).

In some parliamentary systems, the prime minister is a member of the parliament (e.g. in the United Kingdom), whereas in others they are not (e.g. in the Netherlands). They are commonly the leader of the majority party in the lower house of parliament, but only hold the office as long as the "confidence of the house" is maintained. If members of the lower house lose faith in the leader for whatever reason, they can call a vote of no confidence and force the prime minister to resign.

This can be particularly dangerous to a government when the distribution of seats among different parties is relatively even, in which case a new election is often called shortly thereafter. However, in case of general discontent with the head of government, their replacement can be made very smoothly without all the complications that it represents in the case of a presidential system.

The parliamentary system can be contrasted with a presidential system, such as the American congressional system, which operates under a stricter separation of powers, whereby the executive does not form part of, nor is it appointed by, the parliamentary or legislative body. In such a system, congresses do not select or dismiss heads of governments, and governments cannot request an early dissolution as may be the case for parliaments. Some states, such as France, have a semi-presidential system which falls between parliamentary and congressional systems, combining a powerful head of state (president) with a head of government, the prime minister, who is responsible to parliament.