delta (adj./n.)

A symbol ∆ used in some MODELS of TRANSFORMATIONAL GRAMMAR, which acts as a DUMMY element in the generation of DEEP STRUCTURES. The purpose of the delta symbols is to mark the places in an initial PHRASE-MARKER (a PRE-LEXICAL structure) where LEXICAL items are later to be inserted: lexical insertion RULES then replace each ‘empty’ delta by a COMPLEX SYMBOL containing the SYNTACTIC FEATURES which will be used to define the deep structures of the grammar.