This article discusses the natural emergence or later artificial formation of a foreign language in a bilingual individual and the cognitive changes that occur in this process. It presents the views of linguists who have worked in this field, the challenges in forming bilingualism, the learner’s associative thesaurus, and provides answers to the questions of whether bilingualism develops on the basis of one language or emerges from two languages.

Bilingualism, ontogenesis, experimental, linguistic consciousness, psycholinguistic, lexicographic, semantic field, consensus, identification, thesaurus, natural bilingualism, artificial bilingualism, competence, associative.

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