Introduction. The relevance of the study is provoked by the rapid expansion of the educational environment, the emergence of new actors and educational service providers, which indicate changes in the institutional landscape of adult education and the development of educational ecosystems. Both in the world and in Russia, there is a growing demand for bridging the qualification gap and retraining a significant part of adults. Therefore, a comprehensive study of continuing adult education, including formal and informal education, that is inseparable from the demands of the platform economy, is becoming extremely important. There is a tendency to transform the idea of an educational ecosystem for lifelong adult learning into a well-thought-out educational policy. However, the problem is that the scientific and methodological substantiation of the ecosystem approach and the subsequent development of managerial work to develop the quality of human capital education are impossible without a unified terminological language of description.Aim. The article is aimed at theoretical substantiation of the terminological field and interdisciplinary thesaurus modelling of the adult education ecosystem.Methodology and research methods. The methodological basis is framed by evolutionary, systematic and interdisciplinary approaches to analyse adult education with regard to complex socio-economic and digital transformations. Using theoretical methods, such as critical, conceptual, comparative, thematic content analysis of Russian and foreign publications, the authors described the categorical field of the problem under investigation.Results. The authors have found that the conceptual and terminological field of the adult education ecosystem is shaped at the intersection of four disciplinary areas (ecology, economy, education, digital technologies). Based on the results, the authors identified the concepts and categories that reveal the processes in adult education; and proposed the idea of an interdisciplinary thesaurus and its conceptual model. Using the developed thesaurus, the authors gave a theoretical explanation for new phenomena and processes in adult education, carried out comparative analysis of the ecosystem with the traditional system of adult education. The authors define the adult education ecosystem as an open multidimensional self-regulating educational environment, where different types of education (formal, informal, corporate training) integrate via modern digital tools, providing symbiosis and co-evolution of participants, new patterns of links aimed at making a valuable offer for learners.Scientific novelty. For the first time, the idea and model of the interdisciplinary thesaurus have been proposed to describe transformation processes in adult education; the concept of “adult education ecosystem” has been revealed; the peculiarities of the adult education ecosystem in comparison with the traditional education system have been identified. The adult education ecosystem is explained as a theoretical construct, a socio-economic phenomenon and a management paradigm.Practical significance. The proposed thesaurus provides a unified description language that is in demand in pedagogical, managerial and scientific discourses. This is of particular importance for practitioners, designers of educational programmes, methodologists, managers, providers of various educational forms in the context of reforming the national adult education system, synchronising supply and demand in the labour market, developing tools for regulation and support of lifelong learning.
