Presidential form of Government

The presidential system of of government it is a Republican system of government in which head of government is also the head of state and leads executive branch separate from legislative branch . The United States ,for instance have presidential system. The executive is elected and often called "president"and is not responsible to the  legislature and cannot in normal circumstances dismiss it. The legislature we have the right it in extreme cases to dismiss the executive through. However such dismissals are seen so rare  as not to contradict central tenant of presidentialism, that in normal circumstances using normal means the legislature cannot dismiss the executive.

The semipresidential system of government is a mix of presidential and parliamentary system of government in which president and prime minister both are active participant in day to day administration of the state.