This study guide is intended for specialists in the field of philology in higher educational institutions. In the study guide non-reversible lexis and its linguistic features are mainly manifested in translated texts, non-replaceable lexis is used without translation in translated texts, national, local, historical related to the past, way of life, customs and values of a particular people , expression of religious color, having common and different aspects with non-alternative lexical acquisition words, acquisition of some of the non-alternative lexical units into another language under the...