Linguistic diversity has become a hot topic in linguistic research, and a core issue for policy makers and organisations; however, public discourse of linguistic diversity does not normally involve a critical definition ofdiversityitself.Theaimofthisarticleisthentoproposea deconstruction of the notion of linguistic diversity. Starting from a detailed discussion of the very notion of diversity , we will explore the ways in which languages may differ at all levels, focussing on the tension between cross-linguistic trends and variation. We will then discuss the implications of linguistic diversity for language users, and we will tackle the issue of the quantifiability of diversity. Lastly, we will provide an overview of the contributions in this issue.