This paper offers a speculative account of the acquisition of syntactic word class categories by children, based on a notionally founded theory of categories. Categories are differentiated by (non-)possession of simplex semantic features which may combine in varying degrees of complexity. While less complex categories are universal, more complex combinations, such as that characterising adjectives, are not necessarily so. Markedness, or relative accessibility, correlates with relative complexity of representation. With respect to word classes as such, the child's "initial state" is assumed to be undifferentiated, with the first categorisation being based on referentiality. And evolving systems are constrained by a minimality requirement on change of representation which ensures that acquisition of marked categories is late. Initial syntactic structure and its development are built on the basis of the perceived subcategorisation requirements of the emerging word classes.
