Multidisciplinary research is research that involves more than one discipline, but without integration. Results from the involved disciplines are compared and conclusions are subsequently drawn from each of the individual disciplines, but there is no integration of the disciplinary insights.
Interdisciplinary research is research in which relevant concepts, theories, and/or methodologies from different academic disciplines, as well as the results or insights these disciplines generate, are integrated.
Transdisciplinary research occurs when researchers collaborate with stakeholders from outside the academic world. Knowledge from outside the academic world, as well as stakeholder values, is integrated with academic knowledge. Together, these insights determine what problem is studied and how this is done, and which interventions are selected to address the problem.
Although in theory multi-, inter-, and transdisciplinarity can be distinguished, in practice researchers often switch between these approaches – sometimes within the same research project.
Machiel Keestra, and Steph Menken. "Interdisciplinarity." An Introduction to Interdisciplinary Research : Theory and Practice. Amsterdam University Press, 2016. 32. EBSCOhost.