Historically and geographically, the region known as Bosnia (natively Bosna; Cyrillic: Босна) lies mainly in the Dinaric Alps, ranging to the southern borders of the Pannonian plain, with the rivers Sava and Drina marking its northern and eastern borders. The southern, Mediterranean, region of the country is Herzegovina.
The area of Bosnia comprises approximately 41,000 km², and makes up 76% of the territory of the present-day state of Bosnia and Herzegovina. There are now no true borders between the regions in Bosnia and Herzegovina, and, unofficially, Herzegovina is south of Ivan-planina, but its northwestern delimiting is fluid.
The two regions have formed a geopolitical entity since medieval (?) times, and the name "Bosnia" now commonly occurs in historical and geopolitical senses as generally referring to both regions (Bosnia and Herzegovina). The official use of the name including both regions started only in the late period of Ottoman-rule.