The book focusses on the grammatical feature definiteness in German, visible in the inflection of adjectives (ein schön-es Kind vs. das schön-e Kind). It argues for an analysis of this effect that draws a connection to the visible categories of number and gender on nouns and related words rather than an abstract property. This conclusion rests on the conflation of the established grammatical categories into a single one, number-gender, which explains a vast body of grammatical phenomena in German and principles of language in general.