In
linguistics
Linguistics is the scientific study of human language. It is called a scientific study because it entails a comprehensive, systematic, objective, and precise analysis of all aspects of language, particularly its nature and structure. Ling ...
, the head or nucleus of a
phrase is the word that determines the
syntactic
In linguistics, syntax () is the study of how words and morphemes combine to form larger units such as phrases and sentences. Central concerns of syntax include word order, grammatical relations, hierarchical sentence structure (constituency) ...
category of that phrase. For example, the head of the
noun phrase ''boiling hot water'' is the
noun
A noun () is a word that generally functions as the name of a specific object or set of objects, such as living creatures, places, actions, qualities, states of existence, or ideas.Example nouns for:
* Living creatures (including people, alive, ...
''water''. Analogously, the head of a
compound is the
stem
Stem or STEM may refer to:
Plant structures
* Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang
* Stipe (botany), a stalk to support some other structure
* Stipe (mycology), the stem of a mushro ...
that determines the semantic category of that compound. For example, the head of the compound noun ''handbag'' is ''bag'', since a handbag is a bag, not a hand. The other elements of the phrase or compound
modify
Modification may refer to:
* Modifications of school work for students with special educational needs
* Modifications (genetics), changes in appearance arising from changes in the environment
* Posttranslational modifications, changes to prote ...
the head, and are therefore the head's ''
dependents''. Headed phrases and compounds are called ''endocentric'', whereas ''
exocentric'' ("headless") phrases and compounds (if they exist) lack a clear head. Heads are crucial to establishing the direction of
branching. Head-initial phrases are right-branching, head-final phrases are left-branching, and head-medial phrases combine left- and right-branching.
Basic examples
Examine the following expressions:
:::big red dog
:::birdsong
The word ''dog'' is the head of ''big red dog'' since it determines that the phrase is a
noun phrase, not an
adjective phrase. Because the adjectives ''big'' and ''red'' modify this head noun, they are its ''dependents''. Similarly, in the compound noun ''birdsong,'' the stem ''song'' is the head since it determines the basic meaning of the compound. The stem ''bird'' modifies this meaning and is therefore dependent on ''song''. ''Birdsong'' is a kind of song, not a kind of bird. Conversely, a ''songbird'' is a type of bird since the stem ''bird'' is the head in this compound. The heads of phrases can often be identified by way of
constituency tests. For instance, substituting a single word in place of the phrase ''big red dog'' requires the substitute to be a noun (or pronoun), not an adjective.
Representing heads
Trees
Many theories of syntax represent heads by means of tree structures. These trees tend to be organized in terms of one of two relations: either in terms of the ''constituency'' relation of
phrase structure grammars or the ''dependency'' relation of
dependency grammar
Dependency grammar (DG) is a class of modern grammatical theories that are all based on the dependency relation (as opposed to the ''constituency relation'' of phrase structure) and that can be traced back primarily to the work of Lucien Tesni� ...
s. Both relations are illustrated with the following trees:
:::
The constituency relation is shown on the left and the dependency relation on the right. The a-trees identify heads by way of category labels, whereas the b-trees use the words themselves as the labels. The noun ''stories'' (N) is the head over the adjective ''funny'' (A). In the constituency trees on the left, the noun projects its category status up to the mother node, so that the entire phrase is identified as a noun phrase (NP). In the dependency trees on the right, the noun projects only a single node, whereby this node dominates the one node that the adjective projects, a situation that also identifies the entirety as an NP. The constituency trees are structurally the same as their dependency counterparts, the only difference being that a different convention is used for marking heads and dependents. The conventions illustrated with these trees are just a couple of the various tools that grammarians employ to identify heads and dependents. While other conventions abound, they are usually similar to the ones illustrated here.
More trees
The four trees above show a head-final structure. The following trees illustrate head-final structures further as well as head-initial and head-medial structures. The constituency trees (= a-trees) appear on the left, and dependency trees (= b-trees) on the right. Henceforth the convention is employed where the words appear as the labels on the nodes. The next four trees are additional examples of head-final phrases:
:::
The following six trees illustrate head-initial phrases:
:::
And the following six trees are examples of head-medial phrases:
:::
The head-medial constituency trees here assume a more traditional n-ary branching analysis. Since some prominent phrase structure grammars (e.g. most work in
Government and binding theory and the
Minimalist Program
In linguistics, the minimalist program is a major line of inquiry that has been developing inside generative grammar since the early 1990s, starting with a 1993 paper by Noam Chomsky.
Following Imre Lakatos's distinction, Chomsky presents minim ...
) take all branching to be binary, these head-medial a-trees may be controversial.
X-bar trees
Trees that are based on the
X-bar schema also acknowledge head-initial, head-final, and head-medial phrases, although the depiction of heads is less direct. The standard X-bar schema for English is as follows:
:::
This structure is both head-initial and head-final, which makes it head-medial in a sense. It is head-initial insofar as the head X
0 precedes its complement, but it is head-final insofar as the projection X' of the head follows its specifier.
Head-initial vs. head-final languages
Some language typologists classify language
syntax
In linguistics, syntax () is the study of how words and morphemes combine to form larger units such as phrases and sentences. Central concerns of syntax include word order, grammatical relations, hierarchical sentence structure ( constituenc ...
according to a
head directionality parameter in
word order
In linguistics, word order (also known as linear order) is the order of the syntactic constituents of a language. Word order typology studies it from a cross-linguistic perspective, and examines how different languages employ different orders. C ...
, that is, whether a phrase is ''head-initial'' (= right-branching) or ''head-final'' (= left-branching), assuming that it has a fixed word order at all. English is more head-initial than head-final, as illustrated with the following dependency tree of the first sentence of
Franz Kafka
Franz Kafka (3 July 1883 – 3 June 1924) was a German-speaking Bohemian novelist and short-story writer, widely regarded as one of the major figures of 20th-century literature. His work fuses elements of realism and the fantastic. It typ ...
's ''
The Metamorphosis'':
::
The tree shows the extent to which English is primarily a head-initial language. Structure is descending as speech and processing move from left to right. Most dependencies have the head preceding its dependent(s), although there are also head-final dependencies in the tree. For instance, the determiner-noun and adjective-noun dependencies are head-final as well as the subject-verb dependencies. Most other dependencies in English are, however, head-initial as the tree shows. The mixed nature of head-initial and head-final structures is common across languages. In fact purely head-initial or purely head-final languages probably do not exist, although there are some languages that approach purity in this respect, for instance Japanese.
The following tree is of the same sentence from Kafka's story. The glossing conventions are those established b
Lehmann One can easily see the extent to which Japanese is head-final:
A large majority of head-dependent orderings in Japanese are head-final. This fact is obvious in this tree, since structure is strongly ascending as speech and processing move from left to right. Thus the word order of Japanese is in a sense the opposite of English.
Head-marking vs. dependent-marking
It is also common to classify language
morphology according to whether a phrase is
head-marking or
dependent-marking. A given dependency is head-marking, if something about the dependent influences the form of the head, and a given dependency is dependent-marking, if something about the head influences the form of the dependent.
For instance, in the English
possessive case, possessive marking (''s'') appears on the dependent (the possessor), whereas in
Hungarian possessive marking appears on the head noun:
[See Nichols (1986).]
Prosodic head
In a
prosodic unit
In linguistics, a prosodic unit, often called an intonation unit or intonational phrase, is a segment of speech that occurs with a single prosodic contour ( pitch and rhythm contour). The abbreviation IU is used and therefore the full form is o ...
, the head is the part that extends from the first stressed syllable up to (but not including) the tonic syllable. A high head is the stressed syllable that begins the head and is high in pitch, usually higher than the beginning pitch of the tone on the tonic syllable. For example:
The
↑bus was late.
A low head is the syllable that begins the head and is low in pitch, usually lower than the beginning pitch of the tone on the tonic syllable.
The
↓bus was late.
See also
*
Branching
*
Constituent
Constituent or constituency may refer to:
Politics
* An individual voter within an electoral district, state, community, or organization
* Advocacy group or constituency
* Constituent assembly
* Constituencies of Namibia
Other meanings
* Consti ...
*
Dependency grammar
Dependency grammar (DG) is a class of modern grammatical theories that are all based on the dependency relation (as opposed to the ''constituency relation'' of phrase structure) and that can be traced back primarily to the work of Lucien Tesni� ...
*
Head-driven phrase structure grammar Head-driven phrase structure grammar (HPSG) is a highly lexicalized, constraint-based grammar
developed by Carl Pollard and Ivan Sag. It is a type of phrase structure grammar, as opposed to a dependency grammar, and it is the immediate successor ...
*
Head directionality parameter
*
Head-marking language
*
Phrase
*
Phrase structure grammar
Notes
References
*Chomsky, N. 1995. The Minimalist Program. Cambridge, Massachusetts: The MIT Press.
*Corbett, G., N. Fraser, and S. McGlashan (eds). 1993. Heads in Grammatical Theory. Cambridge University Press.
*Hudson, R. A. 1987. Zwicky on heads. Journal of Linguistics 23, 109–132.
*Miller, J. 2011
A critical introduction to syntax London: Continuum.
*Nichols, J. 1986. Head-marking and dependent-marking grammar. Language 62, 56-119.
*Zwicky, A. 1985. Heads. Journal of Linguistics 21, pp. 1–29.
*Zwicky, A. 1993. Heads, bases and functors. In G. Corbett, et al. (eds) 1993, 292–315.
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Syntactic entities