ABSTRACT
X-BAR theory n (in universal grammar) an approach to syntax, x-bar syntax, which attempts to show the general principles of language rather than deal with the structures of one particular language. The syntax is based on four main lexical categories (see lexical category): verbs, nouns, adjectives and prepositions, which become the heads of phrases, e.g. the noun dog becomes the head of the noun phrase The dog with black ears. To show the structure within each phrase and within the phrase marker of the whole sentence, constituents are marked N, Nc, Ncc etc. (see bar notation).
