Researchers have dealt with the complex issue of a phraseological unit since the first attempts to systematize word combinations by degree of stability. Works by the founder of the phraseology theory Ch. Bally, as well as prominent scientists V.V. Vinogradov, A.V. Kunin,and N.M. Shansky are devoted to this issue. Some scholars, supporters of the equivalence theory, consider phraseological units to be formations identical to words (Alyokhina1979). I. Zykovanotes thatthe theories and approaches that form a traditional view of phraseological meaning have contributed much to the understanding of its essence and to the description of its specifics (Zykova 2016).Others support the theory of the relation between the word and the phraseological unit (Kunin1996), which, in our view, reflects the essence of the problem more adequately. As a more complicated unit, a phraseological unit is able to convey a concept more fully (and thus more accurately) than a word. While designating an object or a person, a feature, a mode of action, etc., a phraseological unit also gives additional information on them. Furthermore, a phraseological expression is much more expressive than lexical, because it is often figurative. To determine the content of a phraseological unit, it is necessary to establish its most characteristic differential features. The constituent components of the phraseological unit, having lost their independent meaning, generally express the meaning of the phraseological unit, which is not derived from the meanings of its components. The first differential feature of a phraseological unit is that it has a special meaningwhich a free word combination does not possess. In structural and semantic terms, phraseological units are more complex entities because the meaning of a phraseological unit is expressed not by one word, but by the obligatory combination of two or more components. The components of a phraseological unit are the prototype words with their own forms of word paradigm, capable of functioning outside the phraseological unit. Phraseological units are characterized by the phenomena of synonymy and antonymy, that is, they are capable Erbe der europäischen wissenschaft Part 7 MONOGRAPH 60 ISBN 978-3-9821783-9-4 of forming independent synonymic sets and antonymic pairs. They are more pronounced in emotional and expressive terms. The presence of components is the second differential feature of a phraseological unit. Components of a phraseological unitare constituent parts, and there are no formal semantic relations and connections between words which exist in ordinary word combinations. Acting as a unity of content and form, a phraseological unit is regarded as an independent unit of language, capable of interacting with other units of language in semantic and grammatical relations, and therefore has grammatical categories, i.e. perform a separate syntactic function. Thus, the presence of grammatical categories in a phraseological unit is also one of its distinct features. The phraseological unit acts in each case as a ready-made form. It is contrasted in language and speech with those units that emerge by the familiar pattern and by certain rules. Reproducibility can be regarded as the most common property for phraseological units that differ in the degree of idiomatic nature, the nature of metaphoricity and grammatical structure. The peculiarity of the phraseological unit is the complete or partial reinterpretation of the meaning formed as a result of the semantic shift of the literal meanings of the variable word groups or components of the phraseological unit. Phraseological units are not created during communication, but are reproduced as a ready-made unit, that is, they are characterized by stability of composition. However, the meaning of any derivative of a particular word is motivated by the meaning of the lexical unit from which it was derived while the meaning of a phraseological unit is not determined by the meaning of its individual components. The semantic scope of the meaning of the phraseological unit does not coincide with the semantic meaning of the word. A small number of lexical and semantic variants limit the semantic structure of a word in three languages. Instead, the semantic structure of phraseological units is much wider and has a higher intensity of expression. The lexical meaning is determined by morphemes, but the extent of their participation in its formation is not the same. Root morphemes carry the main semantic load. The semantic expression role of word-forming affixes is much smaller. Morphemes in word structure have more specialization than the components of the phraseological unit. One can distinguish a separate component in a phraseological unit, which acts as a semantic center and carries the main semantic load (Zhukov 1978s. l.), but its role in the structure of the phraseological unit is significantly different from the root morpheme in the structure of the word. The selection of the semantic center of the phraseological unit helps in compiling the Erbe der europäischen wissenschaft Part 7 MONOGRAPH 61 ISBN 978-3-9821783-9-4 relevant dictionaries. This issue remains complex and phraseological dictionaries often contain references to other phraseological units, whereas in the case of lexical units, alphabetical ordering does not cause much difficulty. Comparing phraseological units with their lexical synonyms, I.M. Vyslobodska rightly remarks that phraseological units and their lexical synonyms express the same meanings differently, that is, they are two different types of nomination (Vyslobodska 2002: 58). Only some phraseological units have one-word lexical correspondences. Sometimes it is impossible to convey the meaning of a phraseological unit in one word. This is usually a phrase, explanatory phrase, or whole sentence, especially when it comes to communicative phraseological units.