This study focuses on the changes that doctoral education has experienced in the last decades and discusses the role of doctoral supervisors. The figure of doctoral supervisor continues to be a subject of much debate; therefore, the aim of this study is to provide a universal, global, and common definition that clearly establishes the roles and functions of doctoral supervisors. Employing a multi-method approach, the study utilized the perspectives of linguistic relativism and prototype theory to understand how linguistic and label diversity may influence the perception and approach to supervisory tasks. We examine a corpus of 55 different labels to refer to "doctoral supervisor." Data was collected from 116 countries, encompassing 47 different languages and 55 distinct labels from Europe, Africa, America, Asia, and Oceania, forming a unique corpus of information. The results reveal a total of 18 functions to be fulfilled by the doctoral supervisor. Additionally, the findings underscore the significance of linguistic influence in conceptualizing the functions associated with the supervisor in various cultural contexts and highlight the necessity for redefining the role of the thesis supervisor. The results hold potential benefits for doctoral schools and supervisors, serving as guidelines for standardizing the functions of the doctoral supervisor.