This document provides an overview of syntax and sentence structure. It defines syntax as the rules for forming sentences stored in our brains. These rules specify word order and grammatical relations. Sentences have hierarchical structure that can be represented in phrase structure trees. Syntactic categories include noun phrases, verb phrases, and prepositional phrases. Well-formed sentences obey phrase structure rules and selectional requirements of heads. Recursive rules allow generation of an infinite number of sentences. Structural ambiguities arise when one string has more than one possible parse tree.