A Dictionary of Linguistics and Phonetics David Crystal

This constituent structure may also be represented using brackets, each analytic
decision being represented by the imposition of a pair of square brackets
at the appropriate points in the construction, e.g. [[the clock] [has stop[-ed]]].
A grammar which analyses sentences wholly in this way, i.e. in terms of a
hierarchy of structural layers, is sometimes called a constituent-structure
grammar; in classical generative linguistics, such an analysis is carried on by
the phrase-structure component of the grammar. The term constituency
grammar will also be encountered, as will the term constituent sentence, referring
to an embedded sentence. Constituent-base grammars need to be distinguished
from those which do not recognize constituents, such as dependency grammar
and word grammar.
The limitations of IC analysis have been much discussed in the linguistics
literature, especially in relation to the greater power of transformational
grammars. IC analysis, for example, is unable to make explicit the relationships
between formally connected sets of sentences (such as active and passive),
nor can it demonstrate the ambiguity involved in several kinds of construction
(a much-discussed example here being it is too hot to eat). But some kind of
constituent analysis is an important feature of most grammatical systems. See
also c-structure.
(2) In non-linear phonology, a term which describes a group of features
which regularly function together as a unit in phonological rules. In this
approach, segments are represented as a hierarchy of node configurations,
in which intermediate nodes are constituents and terminal nodes are feature
values. Elements are grouped into constituents using association lines. Only
feature sets which form constituents may function together in phonological
rules. The approach uses the usual tree terminology of generative grammar:
dependents are viewed as ‘daughters’ of a higher constituent node, and ‘sisters’
of other nodes at the same level within the hierarchy.
constituent-command (v.) see command (2)
constraint 105
constrain (v.)
see constraint
constraint (n.) A term used in linguistics, and especially in generative
grammar, to refer to a condition which restricts the application of a rule,
to ensure that the sentences generated are well formed. For example, in
generative phonology, a distinction can be made between ‘simultaneous’ and
‘sequential’ constraints: the former states the restrictions on the simultaneous
occurrence of features, e.g. a segment cannot be at once [+high] and [+low];
the latter states the restrictions on sequences of features, e.g. whether a language
permits consonant clusters. In generative syntax there are also several
constraints which have to be imposed in order to prevent the derivation of
ill-formed phrase-markers, e.g. constraints on the ordering of rules. For
example, ‘surface structure’ constraints (filters, or ‘output conditions’) refer
to conditions where a characteristic of surface structure decides which phrasemarkers
are well formed; e.g. no phrase-marker containing an internal boundary
symbol can qualify as a well-formed surface structure. Other examples include
island constraints and the co-ordinate structure constraint.