Natural Born Citizen = Citizen From Birth. There are only two types of citizens, citizens at birth, and citizens who went through a naturalization process. If you are a citizen and not naturalized you are a natural born citizen (Rubio, Cruz, Jindal etc).
Then....explain why the "Citizen" was excluded from seeking the presidency after a certain time had gone by [Article II; Section I; Paragraph 5]
There are three categories; Naturalized Citizen, Citizen and Natural Born Citizen. Your own Constitution verifies this by grandfathering "Citizens" from seeking the presidency. Why do you think they did this?