Parliamentary System:A form of government where the executive branch derives its democratic legitimacy from its ability to command the confidence of the legislative branch and is also held accountable to that legislature.
Presidential System:A system of government where an executive branch exists and presides (hence 'presidential') separately from the legislature, to which it is not accountable and cannot, in normal circumstances, dismiss it.
Semi: Presidential System - A system of government in which a president exists alongside a prime minister and a cabinet, with the latter two being responsible to the legislature of a state