Chapter 8 extends the network analysis of argument structure to the analysis of parts of speech. Traditionally, parts of speech are analyzed as classes of lexical items with the same or similar structural properties, but the structural criteria that are used to define the major parts of speech (e.g., the occurrence of certain function words or inflectional affixes) can also be seen as properties of particular slots of constructional schemas. Crucially, while the slots of word class schemas are commonly defined by distributional criteria, they are not merely structural concepts but evoke particular conceptualizations. Combining research from cognitive linguistics with research from typology, the chapter argues that the major parts of speech are best analyzed in the framework of a network model in which particular lexical items are linked to particular word class schemas. The bulk of the analysis is concerned with the three major parts of speech (i.e., nouns, verbs, adjectives), but the chapter also includes a section on grammaticalization that explains how grammatical function words are derived from content words (and demonstratives) in a dynamic network model.