Montenegrin is a name used by a large number of Montenegrins for the Serbo-Croatian language as spoken by Montenegrins; it also refers to an incipient standardized form of the Shtokavian dialect of Serbo-Croatian used as the official language of Montenegro. The same subdialect of Shtokavian is also the basis of standard Croatian, Bosnian, and Serbian, so all are mutually intelligible and are a single language by that criterion, despite being distinct national standards.
Montenegrin became the official language of Montenegro with the ratification of a new constitution on 22 October 2007. The Montenegrin standard is still emerging. Its orthography was established 10 July 2009, with the addition of two letters to the alphabet, though grammar and a school curriculum are yet to be approved.
source
wikipedia.org, omniglot.com & ethnologue.comyounger brothers