User blog comment:Reximus55/Government Series - Introduction/@comment-5169980-20131023181218/@comment-1789156-20131023191242

More specificially a republic actually doesn't have to do with having a president, but rather having a group of representatives who vote on laws, such as Congress in the United States. A presidential system is a republican system of government where a head of government is also head of state and leads an executive branch that is separate from a legislative branch. So the presidental system is a specific type of republic.