The complex and the least studied aspects of terminology include questions of its organization at the level of lexico-semantic paradigm. An important problem that requires a thorough study of various terminological systems is the implementation of the semantic process of synonymy in terminology. Based on this, the article reveals the concept of “terminological synonymy” in the English language. The main attention is given to the generalization of theoretical views on the phenomenon of synonymy in terminology. Various linguists have repeatedly emphasized that a terminological system of a particular language differs from its lexical system in nature and specificity of implementation of the semantic processes. A number of linguists emphasize the general linguistic essence of the term. As a result, the statement is true that the same semantic processes occur in the terminological systems as in the vocabulary of a common language. The opposition lies in the categorical denial of these phenomena in terminological systems. It is important to find out whether the symmetry of sign and meaning should be recognized or eliminated to deprive the term of the opportunity to develop polysemy and be used in a synonymous series. Despite the development of the problem, the issue of synonymy in terminology is among the relevant and not having a clear solution. Most works recognize the fact of existence of synonymy in terminology and it is pointed out that the phenomenon of synonymy in the field of scientific terminology characterizes the initial stage of the existence of terminological systems, the period of their formation, when the choice of the best term has not been made yet.