Found:
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) |