(1) The average of the X-Bar data.

(2) DOUBLE BAR : The average of the X-Bar data.

(3) This widely recognized and highly abstract X-bar schema is commonly known as the X-bar theory .

(4) Government and binding theory: it is the fourth period of development Chomsky's TG Grammar, which consists of X-bar theme: the basis, or the starting point, of the utterance.

(5) Argument structure is projected from lexical semantic structure, and d-structure is projected from argument structure and principles of X-bar theory.