All languages in a multilingual speaker's repertoire exhibit cross-linguistic influence (CLI) in diverse directions as displayed via chosen vowels from two groups' repertoire : the Bilingual group (L1 Polish/L2 Danish) and the Multilingual group (L1 Polish/L2 Danish/L3 English). The sole not spotted CLI line is from L3 to L2. Each constituent language in a posited specific global language system has singular attributes as it is affected by other constituent languages. Sot it is shown that a bilingual group's L1 diverges from the same multilingual group's L1, as the latter has a third constituent language. KEYWORDS: Vowel formants, vowel midpoint, cross-linguistic influence, multilingualism, third language acquisition, Danish, Polish