The concepts and data accumulated to date on bilingualism are summarized and generalized in the article. Bilingualism is the presence of two or more languages in a person’s actual life and operating them whenever necessary, regardless of the level of proficiency and medium of language acquisition (natural or artificial). In the cognitive- psycholinguistic perspective, the study of a foreign/second language is primarily about the goals of language training: with a distinct lag from a first language (top-down training) to gain conceptual knowledge of one’s own and foreign cultures and read cognitively complex works in two languages VS together with a first language from early childhood (bottom-up training) to gain the skills of authentic usage of both languages and be fluent in everyday communication. In in the socio-cultural perspective, in multinational states bilingualism is an objective necessity, provided that it is endoglossic. This is an alternative to the full or partial assimilation of linguistic minorities to the language and culture of the majority. The ideal is not linguocultural assimilation, but mutual integration, the formation of a single nation. As for an external foreign language learnt for international communication, it should be mastered less zealously and generally perceived as a mere substitute for an “international auxiliary language” - a simple code, universal and flexible, to convey a person’s individual and national meanings. Acculturation in the spirit of a foreign culture is excluded, it is optimal to focus on the heritage of the internal, national and indigenous, cultures and literatures and learn them in both national/ethnic languages and a foreign language.