Despite the 'nationalisation' of the language in the four countries, "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", which all means that it is still a pluricentric language. "An examination of all the major 'levels' of language show that BCS is clearly a single language with a single grammatical system."