More than 96% of population of Bosnia and Herzegovina belongs to one of its three autochthonous constituent nations: Bosniaks, Serbs and Croats . The term constituent refers to the fact that these three ethnic groups are explicitly mentioned in the constitution, and that none of them can be considered a minority or immigrant.
While each have their own standard language variant and a name for it, they speak mutually intelligible languages. On a dialectal level, Serbs, Croats and Bosniaks speak a variety of Štokavian dialects: Serbs, Bosniaks and Croats "southern" neo-Štokavian; Croats and Bosniaks "western" neo-Štokavian and Bosniaks and Croats "eastern-Bosnian" old-Štokavian. These dialects are mutually intelligible, but have fixed phonetic, morphological and lexical differences. The question of standard language of Bosnia and Herzegovina is resolved in such a way that three constituent ethnic groups have their educational and cultural institutions in their respective native or mother tongue languages: Bosnian, Croatian and Serbian.
The most easily recognizable feature that distinguishes the three ethnic groups is their religion, with Bosniaks predominantly Muslim, Serbs predominantly Orthodox Christians, and Croats Catholic.
A Y chromosome haplogroups study published in 2005 found that "three main groups of Bosnia-Herzegovina, in spite of some quantitative differences, share a large fraction of the same ancient gene pool distinctive for the Balkan area".
On 12 February 1998, Alija Izetbegović, at the time Chair of the Presidency of Bosnia and Herzegovina, instituted proceedings before the Constitutional Court for an evaluation of the consistency of the Constitution of the Republika Srpska and the Constitution of the Federation of Bosnia and Herzegovina with the Constitution of Bosnia and Herzegovina. The request was supplemented on 30 March 1998 when the applicant specified which provisions of the Entities’ Constitutions he considered to be unconstitutional. The four partial decisions were made in 2000, by which many of articles of the constitutions of entities were found to be unconstitutional, which had a great impact on politics of Bosnia and Herzegovina, because there was a need to adjust the current state in the country with the decision of the Court. There was a narrow majority (5-4), in the favour of the applicant. In its decision, among other things, the Court stated: