Declaration of Rachel J. Watters on Authentication of Publication
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`I, Rachel J. Watters, am a librarian, and the Director of Wisconsin TechSearch
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`This Declaration relates to the dates of receipt and availability of the following:
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`Miller, G.A., Beckwith, R., Fellbaum, C., Gross, D., and Miller,
`K.J. (1990) Introduction to WordNet: an on-line lexical
`database. International Journal of Lexicography, 3(4), 235-244.
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`Declaration of Rachel J. Watters on Authentication of Publication
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`line lexical database ( 1990). Based on this information, the date stamp on the journal
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`title page indicates Introduction to WordNet: an on-line lexical database (1990) was
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`received by the University of Wisconsin-Madison Libraries on January 4, 1991.
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`Date: February 28, 2020
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`

`

`ISSN 0950-3846
`
`: International Journal -of
`
`Lexicography
`
`Volume 3 Number 4
`Winter 1990
`
`Page 3 of 16
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`

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`International Journal of
`Lexicography
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`Editor: Robert Ilson (58 Antrim Mansions, Antrim Road, London NW3 4XU, UK)
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`European Association for Lexicography (EURALEX) - Executive Board:
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`© 1990 Oxford University Press
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`Page 4 of 16
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`

`

`International Journal of
`Lexicography
`Volume 3 Number 4 Winter 1990
`
`Contents
`
`Introduction to WordNet: An On-line Lexical Database.
`George A. Miller, Richard Beckwith, Christiane Fellbaum,
`Derek Gross and Katherine J. Miller
`
`Nouns in WordNet: A Lexical Inheritance System.
`George A. Miller
`
`Adjectives in WordNet. Derek Gross and Katherine J. Miller
`
`English Verbs as a Semantic Net. Christiane Fellbaum
`
`Implementing a Lexical Network. Richard Beckwith and
`George A. Miller
`
`The EURALEX Bulletin
`
`235
`
`245
`
`265
`
`278
`
`302
`
`Oxford University Press
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`Page 5 of 16
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`

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`ey-
`ida
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`a<
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`otiVERSi>,
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`Page 6 of 16
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`Page 6 of 16
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`

`Introduction to WordNet: An
`On-line Lexical Database*
`George A. Miller, Princeton University
`Richard Beckwith, Princeton University
`Christiane Fellbaum, Princeton University
`Derek Gross, University of Rochester
`Katherine J. Miller, Princeton University
`
`Abstract
`
`WordNet is an on-line lexical reference system whose design is inspired by current
`psycholinguistic theories of human lexical memory. English nouns, verbs, and adjectives
`are organized into synonym sets, each representing one underlying lexical concept.
`Different relations link the synonym sets.
`
`Standard alphabetical procedures for organizing iexical information put to(cid:173)
`gether words that are spelled alike and scatter words with similar or related
`meanings haphazardly through the list. Unfortunately, there is no obvious
`alternative, no other simple way for lexicographers to keep track of what has
`been done or for readers to find the word they are looking for. But a frequent
`objection to this solution is that finding things on an alphabetical list can be
`tedious and time-consuming. Many people who would like to refer to a
`dictionary decide not to bother with it because finding the information would
`interrupt their work and break their train of thought.
`In this age of computers, however, there is an answer to that complaint. One
`obvious reason to resort to on-line dictionaries - lexical databases that can be
`read by computers - is that computers can search such alphabetical lists much
`faster than people can. A dictionary entry can be available as soon as the target
`word is selected or typed into the keyboard. Moreover, since dictionaries are
`printed from tapes that are read by computers, it is a relatively simple matter to
`
`• Preparation of these five papers was supported in part by contract N00014-86-K-0492 with
`the Office of Naval Research and in part by a grant from the James S. McDonnell Foundation. The
`work on WordNet was done in collaboration with Amalia Bachman, Marie Bienkowski, Patrick
`Byrnes, Roger Chaffin, George Collier, Michael Colon, Melanie Cook, Fiona Cowie, Brian
`Gustafson, P. N. Johnson-Laird , Yana Kane, Judy Kegl, Benjamin Martin, Elana Messer, Antonio
`Romero, Daniel Teibel, Anton Vishio, Pamela Wakefield, and Benjamin Wilkes. The views and
`conclusions contained herein are those of the authors and should not be represented as official
`policies of ONR, the McDonnell Foundation, or Princeton University.
`Correspondence concerning
`these papers should be addressed
`to George A. Miller,
`Department of Psychology, Princeton University, Princeton, NJ 08544-1010.
`
`International Journal of Lexicography, Vol. 3 No. 4
`
`© 1990 Oxford University Press
`0950-3846/90 $3.00
`
`Page 7 of 16
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`

`236 George A. Miller et al.
`
`convert those tapes into the appropriate kind of lexical database. Putting
`conventional dictionaries on line seems a simple and natural marriage of the old
`and the new.
`Once computers are enlisted in the service of dictionary users, however, it
`quickly becomes apparent that it is grossly inefficient to use these powerful
`machines as little more than rapid page-turners. The challenge is to think what
`further use to make of them. WordNet is a proposal for a more effective
`combination of traditional lexicographic information and modern high-speed
`computation.
`This, and the accompanying four papers, is a detailed report of the state of
`WordNet as of 1990. In order to reduce the unnecessary repetition, the papers
`are written to be read consecutively.
`
`Psycholexicology
`
`Murray's Oxford English Dictonary (1928) was compiled "on historical prin(cid:173)
`ciples" and no one doubts the value of the OED in settling issues of word use or
`sense priority. By focussing on historical (diachronic) evidence, however, the
`OED, like other standard dictionaries, neglected questions concerning the
`synchronic organization of lexical knowledge.
`It is now possible to envision ways in which the omission might be repaired.
`The 20th Century has seen the emergence of psycholinguistics, an interdiscipli(cid:173)
`nary field of research concerned with the cognitive bases of linguistic compe(cid:173)
`tence. Both linguists and psycholinguists have explored in considerable depth
`the factors determining the contemporary (synchronic) structure of linguistic
`knowledge in general, and lexical knowledge in particular - Miller and
`Johnson-Laird (1976) have proposed that research concerned with the lexical
`component of language should be called psycholexicology. As linguistic
`theories evolved in recent decades, linguists became increasingly explicit about
`the information a lexicon must contain in order for the phonological, syntactic,
`and lexical components to work together in the everyday production and
`comprehension of linguistic messages, and those proposals have been incorpo(cid:173)
`rated into the work of psycholinguists. Beginning with word association studies
`at the turn of the century and continuing down to the sophisticated experimen(cid:173)
`tal tasks of the past twenty years, psycholinguists have discovered many
`synchronic properties of the mental lexicon that can be exploited in lexicogra(cid:173)
`phy.
`In 1985 a group of psychologists and linguists at Princeton University
`undertook to develop a lexical database along lines suggested by these
`investigations (Miller, 1985). The initial idea was to provide an aid to use in
`searching dictionaries conceptually, rather than merely alphabetically - it was
`to be used in close conjuction with an on-line dictionary of the conventional
`type. As the work proceeded, however, it demanded a more ambitious
`formulation of its own principles and goals. WordNet is the result. Inasmuch as
`it instantiates hypotheses based on results of psycholinguistic research, Word(cid:173)
`Net can be said to be a dictionary based on psycholinguistic principles.
`How the leading psycholiguistic theories should be exploited for this project
`
`Page 8 of 16
`
`

`

`Introduction to WordNet 237
`
`was not always obvious. Unfortunately, most research of interest for psycholex(cid:173)
`icology has dealt with relatively small samples of the English lexicon, often
`concentrating on nouns at the expense of other parts of speech. All too often,
`an interesting hypothesis is put forward , fifty or a hundred words illustrating it
`are considered, and extension to the rest of the lexicon is left as an exercise for
`the reader. One motive for developing WordNet was to expose such hypotheses
`to the full range of the common vocabulary. WordNet presently contains
`approximately 54,000 different lexical entries organized into some 48,000 sets of
`synonyms (Beckwith, Fellbaum, Gross, and Miller, 1990), and only the most
`robust hypotheses have survived.
`The most obvious difference between WordNet and a standard dictionary is
`that WordNet divides the lexicon into four categories: nouns, verbs, modifiers,
`and function words. Actually, WordNet contains only nouns, verbs, and
`adjectives. Adverbs are omitted on the assumption that most of them merely
`duplicate adjectives; the relatively small set of English function words is
`omitted on the assumption (supported by observations of the speech of aphasic
`patients: Garrett, 1982) that they are probably stored separately as part of the
`syntactic component of language. The realization that syntactic categories
`differ in subjective organization emerged first from studies of word associa(cid:173)
`tions. Fillenbaum and Jones (I 965), for example, asked English-speaking
`subjects to give the first word they thought of in response to highly familiar
`words drawn from different syntactic categories. The modal response category
`was the same as the category of the probe word: noun probes elicited noun
`responses 79% of the time, adjectives elicited adjectives 65% of the time, and
`verbs elicited verbs 43% of the time. Since grammatical speech requires a
`speaker to know (at least implicitly) the syntactic privileges of different words,
`it is not surprising that such information would be readily available. How it is
`learned, however, is more of a puzzle: it is rare in connected discourse for
`adjacent words to be from the same syntactic category, so Fillenbaum and
`Jones's data cannot be explained as association by continguity.
`The price of imposing this syntactic categorization on WordNet is a certain
`amount of redundancy that conventional dictionaries avoid - words like back,
`for example, turn up in more than one category. But the advantage is that
`fundamental differences in the semantic organization of these syntactic catego(cid:173)
`ries can be clearly seen and systematically exploited. As will become clear from
`the papers following this one, nouns are organized in lexical memory as topical
`hierarchies, adjectives are organized as N-dimensional hyperspaces, and verbs
`are oganized by a variety of entailment relations. Each of these lexical
`structures reflects a different way of categorizing experience; attempts to impose
`a single organizing principle on all three would badly misrepresent the
`psychological complexity of lexical knowledge.
`The most ambitious feature of WordNet, however, is its attempt to organize
`lexical information in terms of word meanings, rather than word forms. In that
`respect, WordNet resembles a thesaurus more than a dictionary, and, in fact,
`Laurence Urdang's revision of Rodale's The Synonym Finder (1978) and
`Robert L. Chapman's revision of Roget's International Thesaurus (1977) have
`been helpful tools in putting WordNet together. But neither of those excellent
`
`Page 9 of 16
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`

`

`238 George A. Miller et al.
`
`works is well suited to the printed form. The problem with an alphabetical
`thesaurus is redundant entries: if word Wx and word WY are synonyms, the pair
`should be entered twice, once alphabetized under Wx and again alphabetized
`under WY. The problem with a topical thesaurus is that two look-ups are
`required, first on an alphabetical list and again in the thesaurus proper, thus
`doubling a user's search time. These are, of course, precisely the kind of
`mechanical chores that a computer can perform rapdily and efficiently.
`WordNet is not merely an on-line thesaurus, however. In order to appreciate
`what more has been attempted in WordNet, it is necessary to understand its
`basic design (Miller and Fellbaum, in press).
`
`The Lexical Matrix
`
`Lexical semantics begins with a recogrnt1on that a word is a conventional
`association between a lexicalized concept and an utterance that plays a
`syntactic role. This definition of "word" raises at least three classes of problems
`for research. First, what kinds of utterances enter into these lexical associa(cid:173)
`tions? Second, what is the nature and organization of the lexicalized concepts
`that words can express? Third, what syntactic roles do different words play?
`Although it is impossible to ignore any of these questions while considering
`only one, the emphasis here will be on the second class of problems, those
`dealing with the semantic structure of the English lexicon.
`Since the word " word" is commonly used to refer both to the utterance and
`to its associated concept, discussions of this lexical association are vulnerable to
`terminological confusion. In order to reduce ambiguity, therefore, "word
`form" will be used here to refer to the physical utterance or inscription and
`"word meaning" to refer to the lexicalized concept that a form can be used to
`express. Then the starting point for lexical semantics can be said to be the
`mapping between forms and meanings (Miller, 1986). A conservative initial
`assumption is that different syntactic categories of words may have different
`kinds of mappings.
`Table I is offered simply to make the notion of a lexical matrix concrete.
`Word forms are imagined to be listed as headings for the columns; word
`meanings as headings for the rows. An entry in a cell of the matrix implies that
`the form in that column can be used (in an appropriate context) to express the
`meaning in that row. Thus, entry E1,1 implies that word form F 1 can be used to
`express word meaning M 1 . If there are two entries in the same column, the
`word form is polysemous; if there are two entries in the same row, the two word
`forms are synonyms (relative to a context).
`Mappings between forms and meanings are many:many - some forms have
`several different meanings, and some meanings can be expressed by several
`different forms. Two difficult problems of lexicography, polysemy and syno(cid:173)
`nymy, can be viewed as complementary aspects of this mapping. That is to say,
`polysemy and synonymy are problems that arise in the course of gaining access
`to information in the mental lexicon: a listener or reader who recognizes a form
`must cope with its polysemy; a speaker or writer who hopes to express a
`meaning must decide between synonyms.
`
`Page 10 of 16
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`

`

`Table 1. Illustrating the Concept of a Lexical Matrix: F 1 and F 2 are synonyms;
`F 2 is polysemous.
`
`Introduction to WordNet 239
`
`Word
`Meanings
`
`Mi
`M2
`M3
`
`Fi
`
`E1,1
`
`F2
`
`E1,2
`E2,2
`
`Word Forms
`F3
`
`F"
`
`£3,3
`
`As a parenthetical comment, it should be noted that psycholiguists frequently
`represent their hypotheses about language processing by box-and-arrow dia(cid:173)
`grams. In that notation, a lexical matrix could be represented by two boxes with
`arrows going between them in both directions. One box would be labeled
`"Word Meaning" and the other "Word Form"; arrows would indicate that a
`language user could start with a meaning and look for appropriate forms to
`express it, or could start with a form and retrieve appropriate meanings. This
`box-and-arrow representation makes clear the difference between meaning:
`meaning relations (in the Word Meaning box) and word:word relations (in the
`Word Form box). In its initial conception, WordNet was concerned solely with
`the pattern of semantic relations between lexicalized concepts; that is to say, it
`was to be a theory of the Word Meaning box. As work proceeded, however, it
`became increasingly clear that lexical relations in the Word Form box could not
`be ignored. At present, WordNet distinguishes sharply between semantic
`relations and lexical relations; the emphasis is still on semantic relations
`between meanings, but lexical relations between words are also included.
`Although the box-and-arrow representation respects the difference between
`these two kinds of relations, it has the disadvantage that the intricate details of
`the many:many mappings between meanings and forms are slighted, which not
`only conceals the reciprocity of polysemy and synonymy, but also obscures the
`major device used in WordNet to represent meanings. For that reason, this
`description of Word Net has been introduced in terms of a lexical matrix, rather
`than as a box-and-arrow diagram.
`How are word meanings represented in WordNet? In order to simulate a
`lexical matrix it is necessary to have some way to represent both forms and
`meanings in a computer. Inscriptions can provide a reasonably satisfactory
`solution for the forms, but how meanings should be represented poses a critical
`question for any theory of lexical semantics. Lacking an adequate psychological
`theory, methods developed by lexicographers can provide an interim solution:
`definitions can play the same role in a simulation that meanings play in the
`mind of a language user.
`How lexicalized concepts are to be represented by definitions in a theory of
`lexical semantics depends on whether the theory is intended to be constructive
`
`'
`
`Page 11 of 16
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`

`

`240 George A. Miller et al.
`
`or merely differential. In a constructive theory, the representation should
`contain sufficient information to support an accurate construction of the
`concept (by either a person or a machine). The requirements of a constructive
`theory are not easily met, and there is some reason to believe that the definitions
`found in most standard dictionaries do not meet them (Gross, Keg!, Gildea,
`and Miller, 1989; Miller and Gildea, 1987). In a differential theory, on the other
`hand, meanings can be represented by any symbols that enable a theorist to
`distinguish among them. The requirements for a differential theory are more
`modest, yet suffice for the construction of the desired mappings. If the person
`who reads the definition has already acquired the concept and needs merely to
`identify it, then a synonym (or near synonym) is often sufficient. In other words,
`the word meaning M 1 in Table l can be represented by simply listing the word
`forms that can be used to express it: {F 1, F2 , ... }. (Here and later, the curly
`brackets, '{ ' and '}', surround the sets of synonyms that serve as identifying
`definitions of lexicalized concepts.) For example, someone who knows that
`board can signify either a piece of lumber or a group of people assembled for
`some purpose will be able to pick out the intended sense with no more help than
`plank or committee. The synonym sets, {board, plank} and {board, committee}
`can serve as unambiguous designators of these two meanings of board. These
`synonym sets (synsets) do not explain what the concepts are; they merely signify
`that the concepts exist. People who know English are assumed to have already
`acquired the concepts, and are expected to recognize them from the words listed
`in the synset.
`A lexical matrix, therefore, can be represented for theoretical purposes by a
`mapping between written words and synsets. Since English is rich in synonyms,
`synsets are often sufficient for differential purposes. Sometimes, however, an
`appropriate synonym is not available, in which case the polysemy can be
`resolved by a short gloss, e.g. , {board, (a person's meals, provided regularly for
`money)} can serve to differentiate this sense of board from the others; it can be
`regarded as a synset with a single member. The gloss is not intended for use in
`constructiong a new lexical concept by someone not already familiar with it,
`and it differs from a synonym in that it is not used to gain access to information
`stored in the mental lexicon. It fulfills its purpose if it enables the user of
`WordNet, who is assumed to know English, to differentiate this sense from
`others with which it could be confused.
`Synonymy is, of course, a lexical relation between word forms , but because it
`is assigned this central role in WordNet, a notational distinction is made
`between words related by synonymy, which are enclosed in curly brackets, '{'
`and'}', and other lexical relations, which will be enclosed in square brackets,'['
`and ']'. Semantic relations are indicated by pointers.
`WordNet is organized by semantic relations. Since a semantic relation is a
`relation between meanings, and since meanings can be represented by synsets, it
`is natural to think of semantic relations as pointers between synsets. It is
`characteristic of semantic relations that they are reciprocated: if there is a
`semantic relation R between meaning {x, x', .. . } and meaning {y, y' , ... }, then
`there is also a relation R' between {y, y', .. . } and {x , x', ... }. For the purposes of
`the present discussion, the names of the semantic relations will serve a dual role:
`
`Page 12 of 16
`
`

`

`Introduction to WordNet 241
`
`if the relation between the meanings {x, x', .. . } and {y, y', ... } is called.R, then R
`will also be used to designate the relation between individual word forms
`belonging to those synsets. It might be logically tidier to introduce separate
`terms for the relation between meanings and for the relation between forms , but
`even greater confusion might result from the introduction of so many new
`technical terms.
`The following examples illustrate (but do not exhaust) the kinds of relations
`used to create WordNet.
`
`Synonymy
`From what has already been said, it should be obvious that the most important
`relation for WordNet is similarity of meaning, since the ability to judge that
`relation between word forms is a prerequisite for the representation of
`meanings in a lexical matrix. According to one definition (usually attributed to
`Leibniz) two expressions are synonymous if the substitution of one for the other
`never changes the truth value of a sentence in which the substitution is made.
`By that definition, true synonyms are rare, if they exist at all. A weakened
`version of this definition would make synonymy relative to a context: two
`expressions are synonymous in a linguistic context C if the substitution of one
`for the other in C does not alter the truth value. For example, the substitution
`of plank for board will seldom alter truth values in carpentry contexts, although
`there are other contexts of board where that substitution would be totally
`inappropriate.
`Note that the definition of synonymy in terms of substitutability makes it
`necessary to partition WordNet into nouns, adjectives, and verbs. That is to
`say, if concepts are represented by synsets, and if synonyms must be inter(cid:173)
`changeable, then words in different syntactic categories cannot be synonyms
`(cannot form synsets) because they are not interchangeable. Nouns form
`nominal concepts, adjectives form adjectival concepts, verbs form verbal
`concepts. In other words, the use of synsets to represent word meanings is
`consistent with psycholinguistic evidence that nouns, verbs, and modifiers are
`organized independently in semantic memory. An argument might be made in
`favor of still further partitions: some words in the same syntactic category
`(particularly verbs) express very similar concepts, yet cannot be interchanged
`without making the sentence ungrammatical.
`The definition of synonymy in terms of truth va lues seems to make synonymy
`a discrete matter: two words either are synonyms or they are not. But as some
`philosophers have argued, and most psychologists accept without considering
`the alternative, synonymy is best thought of as one end of a continuum along
`which similarity of meaning can be graded. It is probably the case that
`semantically similar words can be interchanged in more contexts than can
`semantically dissimilar words. But the important point here is that theories of
`lexical semantics do not depend on truth-functional conceptions of meaning;
`semantic similarity is sufficient. It is convenient to assume that the relation is
`symmetric: if x is similar to y, then y is equally similar to x.
`The gradability of semantic similarity is ubiquitous, but it is most important
`for understanding the organization of adjectival meanings.
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`242 George A. Miller et al.
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`Antonymy
`Another familiar relation is antonymy, which turns out to be surprisingly
`difficult to define. The antonym of a word xis sometimes not-x, but not always.
`For example, rich and poor are antonyms, but to say that someone is not rich
`does not imply that they must be poor; many people consider themselves
`neither rich nor poor. Antonymy, which seems to be a simple symmetric
`relation, is actually quite complex, yet speakers of English have little difficulty
`recognizing antonyms when they see them.
`Antonymy is a lexical relation between word forms, not a semantic relation
`between word meanings. For example, the meanings {rise, ascend} and {fall,
`descend} may be conceptual opposites, but they are not antonyms; [rise/fal[J are
`antonyms and so are [ascend/descendj, but most people hesitate and look
`thoughtful when asked if rise and descend, or ascend and fall, are antonyms.
`Such facts make apparent the need to distinguish clearly between lexical
`relations between word forms and semantic relations between word meanings.
`Antonymy provides the central organizing principle for the adjectives in
`WordNet, and the complications that arise from the fact that antonymy is a
`lexical relation with important semantic consequences are better discussed in
`that context (Gross and Miller, this volume).
`
`Hyponymy
`Unlike synonymy and antonymy, which are lexical relations between word
`forms , hyponymy/hypernymy is a semantic relation between word meanings:
`e.g., {maple} is a hyponym of {tree}, and {tree} is a hyponym of {plant}. Much
`attention has been devoted to hyponymy/hypernymy (variously called subordi(cid:173)
`nation/superordination, subset/superset, or the ISA relation). A concept repre(cid:173)
`sented by the synset {x, x' , ... } is said to be a hyponym of the concept represented
`by the synset {y, y', ... } if native speakers of English accept sentences constructed
`from such frames as An xis a (kind of) y . The relation can be represented by
`including in {x, x', .. . } a pointer to its superordinate, and including in {y, y', ... }
`pointers to its hyponyms.
`Hyponymy is transitive and asymmetrical (Lyons, 1977, vol. 1 ), and, since
`there is normally a single superordinate, it generates a hierarchical semantic
`structure, in which a hyponym is said to be below its superordinate. Such
`hierarchical representations are widely used in the construction of information
`retrieval systems, where they are called inheritance systems (Touretzky, 1986): a
`hyponym inherits all the features of the more generic concept and adds at least
`one feature that distinguishes it from its superordinate and from any other
`hyponyms of that superordinate. For example, maple inherits the features of its
`superordinate, tree, but is distinguished from other trees by the hardness of its
`wood, the shape of its leaves, the use of its sap for syrup, etc. This convention
`provides the central organizing principle for the nouns in WordNet.
`
`Meronymy
`Synonymy, antonymy, and hyponymy are familiar relations. They apply widely
`throughout the lexicon and people do not need special training in linguistics in
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`Introduction to WordNet