The Web is an unprecedented enabler for publishing, using and exchanging information at global scale. Virtually any topic is covered by an amazing diversity of opinions, view-points, mind sets and backgrounds. The research project RENDER works on methods and techniques to leverage diversity as a crucial source of innovation and creativity, and designs novel algorithms that exploits diversity for ranking, aggregating and presenting Web content. Essential in this respect is a knowledge model that makes accessible — cognitively to human users as well as computationally to the machine — the diversity in content. In this paper, we present a glossary of relevant terms that serves as baseline to the specification of the Knowledge Diversity Model.