Phrase Structure Rules

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Phrase-structure rules are a way to describe a given language's syntax. They are used to break a natural language sentence down into its constituent parts (also known as syntactic categories) namely phrasal categories and lexical categories (aka parts of speech). Phrasal categories include the noun phrase, verb phrase, and prepositional phrase; lexical categories include noun, verb, adjective, adverb, and many others. Phrase structure rules were commonly used in transformational grammar (TGG), although they were not an invention of TGG; rather, early TGG's added to phrase structure rules (the most obvious example being transformations; see the page transformational grammar for an overview of the development of TGG.) A grammar which uses phrase structure rules is called a phrase structure grammar - except in computer science, where it is known as just a grammar, usually context-free.