A parliamentary democracy differs from a presidential democracy in its structure and function. In a parliamentary system, the executive branch derives its legitimacy from the legislative branch and is dependent on its support, often resulting in a fusion of powers. The head of government, typically the prime minister, is often a member of the legislature. Conversely, in a presidential democracy, the president is elected independently of the legislative body and holds a distinct separation of powers, creating a system of checks and balances. Each system influences how policies are developed and implemented.