Although the problem of synonymy is one of the main categories of structural linguistics, it does not hide the fact that it has many controversial issues. Basically, in order to fully study all the functions and natural phenomena of synonymy, it is necessary to conduct a study of semantics in the form. Although the phenomenon of synonymy is recognized in a separate section of lexicology, its universal character allowed to consider it in all areas of linguistic structure. Regardless of the language in which we speak, we follow for that there is a category of synonyms. The phenomenon of synonymy differs in its function of distinguishing values. And meaning is a linguistic expression of thoughts and cognition, therefore, in linguistic questions, related to meaning, does not fit into fixed formulas within the framework of structural linguistics. In terms of the expansion of human knowledge, dynamic changes in the meaning of the language also lead to its transformation. Therefore, one of the unresolved issues in the phenomenon of synonymy is the term synonyms. The article describes the reasons for the formation of term-synonyms, differences from lexical synonyms and changes in semantic development. The study of terms-synonyms is carried out with the aim of developing the use of national terms. This is due to the fact that even now in the Kazakh language there is an equivalent for foreign terms, the parallel use of the term prevents the unification of the term. The formation of absolute synonymous pairs of terms denoting one and the same concept means that one scientific concept has two titles. Therefore, it is necessary to prove which of the two names was chosen and confirmed as a term. This article also serves this purpose.