Referring to increasing interest in acquisition of English as a foreign language in the 21st century, this research focuses on the need to describe the experience of teaching English as a foreign language in Latvia by investigating the teaching of English as a foreign language since 1920, especially the lexical aspect, and its development to this day (2016). A chronological examination of the development of the subject of foreign languages allows to evaluate positive and negative tendencies, as well as to identify new solutions to more efficient teaching of foreign languages. The novelty of this research is that this is the first time in Latvian linguodidactic study, when the usage of semantic field theory in teaching lexis is investigated. Also novel is that the updated lexical approach in the context of semantic field theory, which might have practical domino effect not only on acquisition of English as a foreign language but also on acquisition of other languages. The problem addressed of the research is that there are no basic researches on acquisition of English as a foreign language in Latvia. There is lack of solutions to theoretical and practical questions about acquisition of lexis in a foreign language. The question, which is discussed in PhD thesis, is whether semantic field theory and lexical approach are adaptable for acquisition of foreign languages in Latvia and whether they can be used for more effective teaching of lexis in English. The subject of this PhD thesis is linguodidactic content of lexis in acquisition of English as a foreign language in Latvia. The main focus is on the lexis of the language learner and more productive acquisition of it. This PhD thesis is interdisciplinary research in that linguodidactic questions and lexical aspects in acquisition of English as a foreign language are examined, and information about acquisition of English in Latvia from 1920 to 2016 is gathered, looking for new solutions for more effective teaching of lexis in a foreign language. The object of the research: lexis in acquisition of English as a foreign language in the environment of the formal education (school, university, adult education). The subject of the research: the development of the linguodidactic model's concept of teaching English lexis in acquisition of a foreign language in Latvia. The aim of the research is to analyse and describe theoretical aspects of lexis and lexical aspect of linguodidactic content of English as a foreign language in Latvia in order to identify new approaches to more effective teaching of lexis in a foreign language.