A Dictionary of Linguistics and Phonetics David Crystal

clear-cut as it seems, as the class of prepositions in English, for example, is
relatively open (e.g. in accordance with, on account of, and many more), and
within the so-called open classes of words there are several closed subsystems,
e.g. auxiliary verbs. But the contrast between ‘open’ and ‘closed’ is widely
recognized.
(5) In early language acquisition studies of the two-word stage of grammatical
development, the term refers to the variable element in a construction,
the other being referred to as the pivot. For example, in the set daddy there, cat
there, drink there, there is the pivot word (a member of a small, ‘closed’ class),
and daddy , etc., are members of an open class. The distinction is of largely
historical interest today.
(6) A term used in the classification of types of juncture or transition,
referring to the features which help to define a word boundary, before silence;
also known as ‘plus juncture’. Open juncture is opposed to close juncture; ‘open
transition’ to ‘close transition’.
open class see open (4), (5)
oppositeness 341
operation (n.) In formalized analyses, a term normally used in its general
mathematical sense of a function whose arguments are all drawn from the
same set. In less formal analyses, it is often used more loosely to refer to any
change or process performed on a linguistic representation. For example, in
grammar, the relationship between present and past tense in English can be
described as an operation which adds the suffix -ed to the stem, as in walk⇒
walk+-ed. rules are one kind of formal operation. See also operator (2).
operator (n.) (1) 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.
(2) 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?).
(3) In role and reference grammar, any of a set of formal items which
govern the behaviour 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.
(4) 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.
oppositeness (n.)
see antonymy, complementary, converseness