In modern linguistics the concepts of "thematic group" and "lexical and semantic group" are often identified.
A. Reformatsky displays lexical and semantic concepts from the term "terminological field".
According to F. Filin within thematic groups are lexical and semantic groups of words. The joint between thematic and lexical and semantic groups of words lies in the fact that they both express the objective reality. The difference between these types is that lexical and semantic groups of words are a product of the laws of lexical semantics, while the theme of words is the presence or absence in any language. Content and thematic content groups depend only on the people knowledge, on the ability to classify aspects of reality that got their verbal designation. Ranging lexical items into thematic groups one should take into account not only the existing name but also those that can complement a particular thematic group.
From all the above it can be concluded that any lexical and semantic and thematic classification of vocabulary is somewhat arbitrary, since between the selected groups there are no definite boundaries. This demonstrates the open character of lexical and semantic groups.