The paper proposes that there is a *ABA morphological constraint on the marking of mass, count and plural denotations. I interpret this in terms of nesting structures, taking the mass denotation to be basic, with count nouns derived by a special head from the mass denotation, and the plural most complex (as in Borer 2005). I also focus on the fact that syncretism patterns among mass/count/plural denotations are influenced by case (structural vs. oblique), so that in some languages it looks like numerals combine with the plural in structural cases, and singular in obliques (or vice versa). The paper discusses data from (in no particular order) Estonian, North and South Saami, Finnish, Dutch, Russian, Serbian, Turkish, Digor Ossetic, Czech.