operator (n.)

In FORMAL SEMANTICS, a term used in two main ways: (a) referring to any symbol or EXPRESSION which can BIND a VARIABLE, such as the universal or existential QUANTIFIERS or the LAMBDA binder (‘variable binding operators’); (b) referring to any symbol or expression which denotes an OPERATION (or more loosely, any FUNCTION), especially if it is a LOGICAL CONSTANT.

In some approaches to English GRAMMAR (notably QUIRK GRAMMAR), the first AUXILIARY VERB to be used in a verb phrase. It is so called because it performs an operation on the CLAUSE, such as marking the change from STATEMENT to QUESTION. For example, in The cat has been eating, has is the operator (cf. Has the cat been eating?).

In ROLE AND REFERENCE GRAMMAR, any of a set of formal items which govern the behavior of units in interCLAUSAL construction. Examples include ASPECT, which affects the VERB; MODALITY, which affects the CORE part of the clause; and TENSE, which affects the clause PERIPHERY.

In GOVERNMENT-BINDING THEORY, a notion that applies to several TRANSFORMATIONS (e.g. WH-movement, RELATIVE clause formulation, TOUGH-movement, CLEFTING and TOPICALIZATION) that have properties in common – namely, they leave a GAP and obey the SUBJACENCY condition. Because they all involve the same MOVEMENT operation, the constructions derived in this way are called operator constructions.