The dialects of Serbo-Croatian include the regional varieties of Serbo-Croatian as a whole or as part of its standard varieties: Bosnian, Croatian, Montenegrin and Serbian. They are part of the dialect continuum of South Slavic languages that joins the Macedonian dialects on south, Bulgarian dialects on southeast and Slovene dialects on northwest. Grouping of several dialects as "dialects of Serbo-Croatian" is purely a convenience, because there are no features that are common to all of them and only to them.