text: Also, the contemporary situation is unstable with regard to the accentuation, because phoneticians have observed that the 4-accents speech has, in all likelihood, shown to be increasingly unstable, which resulted in proposals that a 3-accents norm be prescribed. This is particularly true for Croatian, where, contrary to all expectations, the influence of Chakavian and Kajkavian dialects on the standard language has been waxing, not waning, in the past 50–70 years.
  The Croatian, Serbian, and Bosnian standard variants, although all based on the East Herzegovinian subdialect of Neo-Shtokavian and mutually intelligible, do differ slightly, as is the case with other pluricentric languages (English, Spanish, German and Portuguese, among others), but not to a degree which would justify considering them as different languages. Their structures are grammatically and phonologically almost identical, but have differences in vocabulary and semantics: "Lexical differences between the ethnic variants are extremely limited, even when compared with those between closely related Slavic languages (such as standard Czech and Slovak, Bulgarian and Macedonian), and grammatical differences are even less pronounced. More importantly, complete understanding between the ethnic variants of the standard language makes translation and second language teaching impossible." See Differences between standard Bosnian, Croatian and Serbian.
  In 2017, numerous prominent writers, scientists, journalists, activists and other public figures from Croatia, Bosnia and Herzegovina, Montenegro and Serbia signed the Declaration on the Common Language, which states that in Croatia, Serbia, Bosnia and Herzegovina and Montenegro a common polycentric standard language is used, consisting of several standard varieties, similar to the situation in German, English, or Spanish.