Roots and Affixes is an investigation into the primitives of syntax. It focuses on the lexical projection and the categorial head. Accordingly, it consists of two parts. The first part argues that the features of lexical vocabulary items (such as light and kiss) are not an active part of the syntactic derivation. The author provides empirical support for the claim that vocabulary items are inserted post- syntactically, adopting the view that syntax operates on UG-features only. She argues that the root terminal node is a by-product of the operation Merge that is characterized by the mere absence of features. It is further shown that functional structure determines subcategories of lexical items. In the second part of the thesis it is argued that categorial heads do not exist. As a result, derivational affixes do not realize categorial heads. The author proposes instead that derivational affixes are lexical vocabulary items which realize root positions. It is shown that the abandonment of categorial heads does not lead to a loss of explanatory adequacy. The general conclusion is that lexical categorial features are not a primitive of syntax.