This article addresses the problem of equivalence in translation. The analysis is based on the provisions of A.D. Schweitzer, who takes three dimensions of semiosis as a basis: (sign process), distinguished in semiotics: syntactics (sign: sign relationship), semantics (sign: referent relationship) and pragmatist (sign: person relationship). The purpose of this article is to consider the semantic type of equivalence on the material of popular science texts. In the process of analysis, it was found that it is advisable to study the semantic type of equivalence as the relationship between the units of the original text and the translation text at the level of the word value. The preservation of the semantic type of equivalence implies the preservation of the semantic invariant. Preliminary conclusions were drawn that not always stable interlanguage lexical correspondences are pragmatically equivalent translation correspondences and, on the contrary, translation correspondences, which with a lesser degree of probability can be attributed to stable, regular interlanguage correspondences, are pragmatically equivalent, equivalent. These conclusions can be further used not only in the theory and practice of translation, but also in such a promising branch of the theory and practice of translation as the assessment of the quality of a translation.