A parliamentary system, or parliamentary democracy, is a form of government based on the fusion of powers. In this system the head of government (chief executive) derives their democratic legitimacy from their ability to command the support ("confidence") of a majority of the parliament, to which they are held accountable. This head of government is usually, but not always, distinct from a ceremonial head of state. This is in contrast to a presidential system, which features a president who is not fully accountable to the legislature, and cannot be replaced by a simple majority vote.
Countries with parliamentary systems may be constitutional monarchies, where a monarch is the head of state while the head of government is almost always a member of parliament, or parliamentary republics, where a mostly ceremonial president is the head of state while the head of government is from the legislature. In a few countries, the head of government is also head of state but is elected by the legislature. In bicameral parliaments, the head of government is generally, though not always, a member of the lower house.
