This document discusses the rules of syntax in language. Syntax refers to the rules governing how words are combined to form sentences. While an infinite number of sentences can be formed by adding words, there are rules that determine how words are ordered to convey meaning. For example, the typical word order in English is subject-verb-object. Syntactic rules also help identify constituents, or groups of words, within a sentence and their roles. Constituents can be tested by their ability to stand alone or be replaced by a pronoun. Understanding syntax allows sentences to be broken down and analyzed in a hierarchical structure like a tree diagram.