The terminological synonyms base Terminological Synonyms of the Lithuanian Language is a product of the Institute of the Lithuanian Language. The base contains synonymic lines of terms of different (international, Lithuanian and hybrid) origin that can be found in Lithuanian glossaries and dictionaries of terms and special encyclopaedias from different fields.

Terminological synonyms can be looked up in the base alphabetically. Articles of terms may include definitions and equivalents of terms in other languages. The structure of term articles depends on the source. Definitions are available for terms found in glossaries and encyclopaedias. Terms provided in dictionaries come with their equivalents in foreign languages.