The composition of information law’s terminological lexicon requires a comprehensive study in view of its diversity. The article attempts a linguistic characterization of professionalisms and nomens as important functional elements of the specific vocabulary of the informational and legal field. The purpose of the article is to clarify the specifics of different types of special lexemes (nomens and professionalisms) in informational and legal discourse in comparison with the main lexical unit of the terminological system – the term, which involves the analysis of established views of linguists and new trends in terminological studies regarding the studied types of special vocabulary, the linguistic interpretation of professionalism and the nomenclature unit of scientific style. It has been established that in the speech of specialists, professionalisms verbalize special knowledge, and act as synonymous professional‑conversational doublets, name realities and convey special information. They appear in use, replacing officially recognized terms and adapting themselves to oral collective communication. It was found that professionalisms not codified in dictionaries often penetrate into written speech during the coverage of topical issues by journalistic publications or professionally oriented texts. As part of the terminology of information law, a special group has been identified and classified – nomens, which denote single names, most often their own. It was found that they reveal certain difficulties for codification, since a new nomen is not always accompanied by a characteristic. The presence of professionalisms and nomens in information and legal discourse is quite obvious and is explained by the functional expediency of the names used by specialists in special communication.