In this chapter, we show that the well-formedness of each phrase depends on its internal and external syntax. The pivotal daughter element is the head, which determines what expressions may accompany it as its syntactic sisters. We observe that a grammar with simple phrase-structure rules raises two important issues: endocentricity (headedness) of a phrase and redundancies in the lexicon. To resolve these two issues, generative grammar has introduced X’ rules, including three key combinatorial rules: head-complement(s), head-specifier, and head-modifier. These rules ensure that each phrase is a projection of a head expression, while recognizing the existence of intermediate phrases (X’ phrases). X’ syntax captures the similarities between NPs and Ss by treating these phrase types in a uniform way. The grammar we adopt in this book (SBCG) follows this direction by using a fine-grained feature system to describe the syntactic and semantic properties of both simple and complex signs. This chapter introduces the basic feature system that we will use in describing the English language. We also examine the patterns of semantic-role expression called argument-structure patterns.