left-branching (adj.)

A term used in GENERATIVE GRAMMAR to refer to a CONSTRUCTION whose complexity is represented on the left-hand side of a TREE diagram. The type of RULE involved can be represented by X ⇒ (X) + Y. For example, the phrase my friend’s aunt’s pen is a ‘left-branching’ or ‘left RECURSIVE’ structure; it contrasts with the RIGHT-BRANCHING character of the pen of the friend of my aunt. Within classical TRANSFORMATIONAL grammar, the left branch constraint/condition asserts that no element on the left branch of another noun phrase may be extracted from that noun phrase. The condition accounts for the unacceptability of English sentences such as *How many did you read – books?, in which an adjective phrase has been extracted out of the noun phrase headed by books.