SUMMARY
The article analyzes microgroup of terms relating to the process of second language acquisition or foreign language learning (language aptitude, interlanguage, language competence, language performance, language proficiency). The semantics of this group is analyzed and some aspects of normalization (compliance with linguistic and terminological norms) and harmonization (compliance with variants that function in English) are proposed.The difference between the terms of language acquisition and language learning is specified. The author of the article proves the idea that the acquisition of the second language is an unconscious process of producing the language, when a person implicitly assimilates speech samples and produces them intuitively. Learning a foreign language is a conscious process of producing a language when a person explicitly learns speech samples and produces them consciously.Language aptitude denotes the innate ability of a person which develops with the experience of communication, and it is a kind of mechanism that allows the mental and physiological levels to master the language.It is revealed that bilingualism (natural and educational) can be the result of different strategies of language mastering and thus there are various mechanisms for its formation. It is found out that interlanguage is a language that is characterizing a person who learns a new language, and it is the result of the interaction of language systems, rules, norms of native language and the language which is learned. It is dynamic and reflects the appropriate level of language proficiency.The relationship between terms language competence (a set of language knowledge), language performance (production and comprehension of language), and language proficiency (ability of an individual to speak or perform in a language according to the aim of communication) is determined. These terms are at the stage of entry into Ukrainian science.