Only in recent decades in nomenclature has attention been paid not only to nouns but also to other part of speech. Therefore, systematic studies are needed to more closely determine the terminological role of verbs, adverbs and adjectives, and this paper is a contribution to these efforts. The theoretical part of the paper describes modern theories of terminology, the problem of adjective categorization and describes the features of Croatian medical terminology within which adjectives are studied. The development of the Croatian medical language is described with the emphasis on the importance of the existence of communication registers in this area, which is why the appearance of synonyms, i.e. terminological variants, is frequent. It is emphasized that the basis of the medical language is Greek and Latin and that in the Croatian medical language internationalisms and adjectives of domestic origin coexist. Special attention is paid to English terms, which have become the lingua franca of the medical field. In the second part of the paper, an individual analysis of the two corpora assembled in the Sketch Engine tool was done. The research conducted was a corpus-based analysis of terms and their collocations. Two corpora have been compiled – the scientific corpus, which consists of relevant medical journals, and the popular corpus, which includes popular web portals. The process of collection of materials for the corpus and the way in which the corpus was composed was described, and then there were listed the singled-out one-word adjective terminological candidates and multi-word terminological candidates with an adjective component, which were manually evaluated. A semi-automatic method of extraction was applied, which meant that after the automatic extraction of the most frequent adjectives from the corpus of scientific and professional-popular texts, an exhaustive examination of both corpora followed. Through careful reading of longer sections of the text, terminological candidates as possible terms were found. The process of determining the termhood of adjectives was very complex – the status of adjectives in the conceptual system of the medical field was sought to be determined through the conceptual connections it made with other concepts of the domain. The obtained linguistic material was reviewed according to the established criteria of naming, which are the existence of a definition, the relevance of meaning in a given area and collocation potential. However, we do not consider the proposed criteria of adjective naming unquestionable and unambiguous, so methodological doubts arose as to which criterion must be met for an adjective to function as a term, i.e. whether all three criteria need to be met. Based on the analysis of the singled-out terminological candidates, we concluded that the criteria of definition and relevance of meaning are necessary for an adjective to function as a term, so we have accordingly suggested our own definition for some of the one-word adjective candidates for which we did not find a definition in the general dictionary and Struna and whose meaning we find relevant in the medical field. We believe that the corpus size of about 10 million occurrences contributed to obtaining better research results because we relied less on our own linguistic intuition and knowledge of the domain, and more on examples, i.e. evidence of individual theses that are corpus-based. Relevant medical journals were included in the scientific corpus, and online portals dealing with health topics were included in the corpus of popular texts. A large number of the most frequent adjectives and adjective-noun conjunctions have been singled out, and the important role of adjectives in the formation of medical terms and their classification within the taxonomy has been established. The theoretical framework of modern theories of terminology is justified by the fact that it has been concluded that in determining the termhood of an adjective it is inevitable to include the context in which it appears. It has been shown that adjectives in medical terminology are an important component of multi-word terms, and the analysis of collocation potential sought to determine the values of attributes by which members of a particular semantic class differ. A comparative analysis of the scientific corpus and corpus of popular texts was also carried out in order to highlight the similarities and differences of adjectives in different registers of Croatian medical terminology. We conducted an individual and comparative analysis of the scientific and popular corpus to obtain a comprehensive picture of the similarities and differences of these two communication registers in the medical branch. Within this approach, we placed adjective units and concluded that our research confirms that the background of determining the term of a unit is context, i.e. that meaning cannot be observed in isolation, but that use is an inevitable component of determining meaning. With this paper we wanted to prove that terminological units also have a place in general language, not only in a narrowly specialized register, because information is transmitted in heterogeneous communication situations, which affects the dynamism of the terminological unit. The terminological and general linguistic system are interdependent because the term appears in a syntagmatic environment with terminological and general linguistic units. Adjectives cannot be analysed in isolation, but in a syntagmatic environment, so the dynamic terminological description based on the description of key processes and events in the field of specialized knowledge such as medicine, which is used in frame-based theory of terminology, was extremely valuable to describe conceptual relationships between categories of specialized knowledge in the field of medicine. The starting point was the assumption that in the scientific register internationalisms prevail over adjectives of domestic origin, and it was determined whether adjectives of domestic origin, which were given priority over international adjectives in the Croatian professional terminology database Struna, actually came to use. By emphasizing that many international adjectives have good domestic adjective substitutes, which is shown in the table of synonymous versions as an appendix to the paper, the aim was to contribute to the further popularization of Croatian terms in the medical field. The paper proposes a model of semantic categorization of adjectives in medical terminology according to the type of terms they name and define in more detail. The semantic categorization of adjectives in Croatian medical terminology based on the groups of terms they describe and define is also proposed, and the Dixon classification (Dixon 1999, 2004) and the classification applied in the construction of the EcoLexicon database (2019) served as a starting point. From these two classifications we have taken the types of meaning that we consider applicable in the medical field and added to them meanings relevant to the medical field such as outcome/result and source. We thus established prototypical semantic attributes for the most important conceptual categories in the medical field, and decided on the meaning of adjectives on the basis of their relationships with entities. The research results are applicable in practical terminology and translation theory and practice, and will contribute to the development of terminological research, improvement of applied terminographic methods and better understanding of the relationship between general and specialized knowledge. The goals of the research: 1. to investigate and describe the role of adjectives in professional language on the example of Croatian medical terminology 1. to determine the criteria under which adjectives function as terms and explore and describe the semantic relationships between them 2. to propose a classification of adjectives in Croatian medical terminology based on the type of terms they name and specify. The hypotheses of the research: 1. High structure of medical terms is the starting point for the classification of adjectives in the language of the medical profession. 2. There will be more international adjectives in the corpus of scientific texts than in the corpus of popular texts. 3. The collocation potential of adjectives changes with respect to the scientific and popular corpus. In this paper, the role of adjectives in Croatian medical terminology is researched within the framework of modern theories of terminology – communicative theory of terminology (Cabré 1999, 2003), sociocognitive theory of terminology (Temmerman 2000) and frame-based theory of terminology (Faber 2009) – whose features are described in detail whereby it was pointed out why adjectives will not be studied within the traditional terminological approach. It is argued that the lexical unit is context dependent and that discourse is important in describing the relationship between a concept and a term because the specialized meaning of a lexical unit is realized in use. The adjectives are analysed from the perspective of general and specialized language. A complex categorization of adjectives is given as stated in grammar manuals, and the relation of adjectives to nouns and verbs is analysed. The termhood of adjectives is problematized, and finally it is pointed out that adjectives are mostly a component of multi-word terms. At the end of the paper there are two appendices. Appendix 1 provides a table with an alphabetical list of international and domestic versions of adjectives and the collocations and domains in which they occur, and Appendix 2 lists the most common adjectives in the scientific and popular corpus. Corpus methods provide important insights into the lexicalization of key terms in the medical field. The combination of automatic and manual methods and the stratification of corpus methodological procedures resulted in a representative number of adjectives, and conclusions based on their analysis can serve as a starting point in further research. The results of the research contribute to terminological and terminographic research and medical language, proving the justification of the need to give much more attention to adjectives in terminology because they participate in building knowledge of relevant structures and form one-word and multi-word terms. The results of this paper can be applied in the design of terminological resources for professionals and translators by using an appropriate form of the term based on the frequency of collocation connections. The results can also be used in the preparation of monolingual and multilingual corpora on which modern machine translation systems are based. We therefore believe that this paper is part of linguistic research whose results are a concrete application in the development of language resources. This paper provides a good basis for further research of adjectives in the nomenclature of other professional domains and is the first comprehensive overview of the role of adjectives in nomenclature in Croatian scientific literature. The aim of this paper was to illustrate the multidimensionality and terminological status of adjectives and we certainly hope that they will contribute to their inclusion in professional terminological manuals.