The usefulness of the term “encyclopaedia” in the study of pre-modern Arabic and Islamic literature has been the subject of some discussion over the last decade. The main concern has been that it is applied to a wide range of texts and text-types in a vague and inflationary manner, leaving the intended meaning unclear in any given case. Although there is much merit to this criticism, the discipline also knows of more systematic usages. This paper surveys some of these, arguing that although the label “encyclopaedia” indeed has its disadvantages, the analytical concepts and categories lying behind a usage are of greater importance than the choice of term itself. In light of these arguments, some of the most prominent scholarly usages of encyclopaedia and encyclopaedism in regard to the fourth Islamic century/tenth century CE are assessed.