Discipline is commonly used to denote particular areas of knowledge, research and education. Yet, the concept is often not very well defined or even explicitly discussed when used in knowledge organization and related fields. The aim of this article is to encourage and facilitate further reflections on academic disciplines, while at the same time offering insights on how this elusive concept might be understood. An overarching argument is that discipline should foremost be understood in relation to institutional and organizational features and this is what distinguishes it from related terms such as, field, domain or topic. The paper reviews the etymology and history of the concept, it discusses attempts to define and conceptualise disciplines and it offers insights on how disciplines can be studied. Regardless of our views of disciplines, either as inherently out-dated constructs or as important features of a well-functioning academia, it is concluded that further precision or care in explicating the concept is needed.