The article studies the development process of medical informatics specialty terminology as the ground for further research into foreign countries' experience, including the Canadian one, of specialists' professional training in the field of MI. The study determines the origin and chief stages of the formation and development of the medical informatics terminological system. The author performs the comparative analysis of terms used by the world organizations on health care informatisation issues, particularly International Medical Informatics Association as well as medical informatics associations of the USA and Canada as the leading countries where qualified workforce in the medical informatics specialty is trained. The European and Ukrainian experience has also been taken into consideration. The results of the comparative study have shown that the English terms "medical informatics", "biomedical informatics" and "health informatics" serve as the umbrella terms for professional training programs and include a set of subspecialties that identify diverse spheres of information technology applications to medical science and practice, namely "clinical informatics", "bioinformatics", "health care informatics", "nursing informatics", "imaging informatics", etc.