Definition & Meaning of "X-bar theory"

What is "X-bar theory"?

X-bar theory is a component of generative grammar that analyzes the structure of phrases within a sentence. Developed by Noam Chomsky, this theory proposes that phrases are organized in a hierarchical manner, with a central element known as the "head" and additional constituents that can be added as complements or modifiers. The theory uses a series of levels, referred to as "X-bar levels", to represent these structures, allowing for the systematic organization of different types of phrases, such as noun phrases and verb phrases. X-bar theory helps to explain the relationships between elements in a phrase and provides insights into the syntactic structure of languages.