This volume explores the expression of the concepts count and mass in human language and probes the complex relation between seemingly incontrovertible aspects of meaning and their varied grammatical realizations across languages. In English, count nouns are those that can be counted and pluralized (two cats), whereas mass nouns cannot be, at least not without a change in meaning (#two rices). The chapters in this volume explore the question of the cognitive and linguistic universality and variability of the concepts count and mass from philosophical, semantic, and morpho-syntactic points of view, touching also on issues in acquisition and processing. The volume also significantly contributes to our cross-linguistic knowledge, as it includes chapters with a focus on Blackfoot, Cantonese, Dagaare, English, Halkomelem, Lithuanian, Malagasy, Mandarin, Ojibwe, and Persian, as well as discussion of several other languages including Armenian, Hungarian, and Korean. The overall consensus of this volume is that while the general concepts of count and mass are available to all humans, forms of grammaticalization involving number, classifiers, and determiners play a key role in their linguistic treatment, and indeed in whether these concepts are grammatically expressed at all. This variation may be reflect the fact that count/mass is just one possible realization of a deeper and broader concept, itself related to the categories of nominal and verbal aspect.