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empty operator

SYNTAX: Operator without phonological content. EXAMPLE: in (i) the 'implicit relative pronoun' is an empty operator binding the variable t.

(i) the man [CP Oi [IP you fired ti yesterday]]
An empty operator has also been postulated for Parasitic gap constructions and Tough-movement constructions.
LIT. Chomsky, N. (1982)
Haegeman, L. (1991)