1 LING 62n Autumn 2008 LINGUIST 62n Language and Food Background Lecture: Word Meaning Oct 2, 2008 Dan Jurafsky

1LING 62n Autumn 2008

LINGUIST 62nLanguage and Food

Background Lecture: Word Meaning

Oct 2, 2008Dan Jurafsky


Two topics today

The intuitive idea of a “word sense”Defining relations between “word senses”More carefully defining a word sense


First idea: The unit of meaning is called a Sense or wordsense

One word “bank” can have multiple different meanings:

“Instead, a bank can hold the investments in a custodial account in the client’s name”“But as agriculture burgeons on the east bank, the river will shrink even more”

We say that a sense is a representation of one aspect of the meaning of a word.Thus bank here has two senses

Bank1:Bank2:


Complex relationships between words and senses

Homonyms:Two words that have the same form

– Sound the same (phonological form), written the same (orthographic form) or both

But have unrelated, distinct meaningsClear example:

– Bat (wooden stick-like thing) vs– Bat (flying scary mammal thing)– Or bank (financial institution) versus bank (riverside)

Can be homographs (bat, bank), homophones (below), or both:

– Homophones: Write and right Piece and peace


Polysemy

1. The bank was constructed in 1875 out of local red brick.2. I withdrew the money from the bank Are those the same sense?We might call sense 1:

“the building belonging to a financial institution”

Or consider the following exampleWhile some banks furnish sperm only to married women, others are less restrictive

Which sense of bank is this?


Polysemy

We call polysemy the situation when a single word has multiple related meanings (bank the building, bank the financial institution, bank the biological repository)Most non-rare words have multiple meanings


Polysemy: A systematic relationship between senses

Lots of types of polysemy are systematicSchool, university, hospitalCan all be used to mean the institution or the building.

We might say there is a relationship:Building <-> Organization

Other such kinds of systematic polysemy:


How do we know when a word has more than one sense?

Consider examples of the word “serve”:Which flights serve breakfast?Does America West serve Philadelphia?

The “zeugma” test:

?Does United serve breakfast and San Jose?

Since this sounds weird, we say that these are two different senses of “serve”


Other relationships between word meanings

SynonymyAntonymyHypernomyHyponomyMeronomy


Synonyms

Word that have the same meaning in some or all contexts.

filbert / hazelnutcouch / sofabig / largeautomobile / carvomit / throw upWater / H20

Two lexemes are synonyms if they can be successfully substituted for each other in all situations

If so they have the same propositional meaning


Synonyms

But there are few (or no) examples of perfect synonymy.

Why should that be? Even if many aspects of meaning are identicalStill may not preserve the acceptability based on notions of politeness, slang, register, genre, etc.

Example:Water and H20

Big/largeBrave/courageous


Synonymy is a relation between senses rather than words

Consider the words big and largeAre they synonyms?

How big is that plane?Would I be flying on a large or small plane?

How about here:Miss Nelson, for instance, became a kind of big sister to Benjamin.?Miss Nelson, for instance, became a kind of large sister to Benjamin.

Why?big has a sense that means being older, or grown uplarge lacks this sense


Antonyms

Senses that are opposites with respect to one feature of their meaningOtherwise, they are very similar!

dark / lightshort / longhot / coldup / downin / out

More formally: antonyms candefine a binary opposition or at opposite ends of a scale (long/short, fast/slow)Be reversives: rise/fall, up/down


Hyponymy

One sense is a hyponym or subordinate of another if the first sense is more specific, denoting a subclass of the other

car is a hyponym/subordinate of vehicledog is a hyponym/subordinate of animalmango is a hyponym/subordinate of fruit

Converselyvehicle is a hypernym/superordinate of caranimal is a hypernym/superordinate of dogfruit is a hypernym of mango

superordinate

vehicle fruit furniture mammal

subordinate car mango chair dog


Hypernymy more formally

Extensional:The class denoted by the superordinateextensionally includes the class denoted by the hyponym

Entailment:A sense A is a hyponym of sense B if being an A entails being a B

Hyponymy is usually transitive (A hypo B and B hypo C entails A hypo C)


WordNet

An on-line thesaurus/dictionaryhttp://www.cogsci.princeton.edu/cgi-bin/webwn


Format of Wordnet Entries


WordNet Noun Relations


WordNet Hierarchies


Now that we’ve talked about relations between senses

How do we define the sense of a word?


Chicken in the American Heritage Dictionary

1a. The common domestic fowl (Gallus domesticus) or its young. 1b. Any of various similar or related birds. 1c. The flesh of the common domestic fowl.

2. Slang A coward.

3. Any of various foolhardy competitions in which the participants persist in a dangerous course of action until one loses nerve and stops.


But can we define the meaning of these word senses?

From the American Heritage:

These definitions are kind of circularFine for informal use. But can we do better?


Classical theories of word meaning

What is the meaning of the word “square”?Four Necessary and sufficient conditions1. A closed flat figure2. Having four sides3. All sides are equal in length4. All interior angles are equal

Sometimes called a Checklist theory of meaning


How about the words “hen”, “rooster”, “chick”

+gallus domesticus+male+adult


What about the word “game”?

No necessary and sufficient conditionsNo common propertiesEven though each exemplar of games resembles each otherWe say that the concept “game” is defined more by family resemblance than by checklist.


Name these items

Slide from Joel Cooper, University of Utah


Basic Level Categories

chair office chair piano chair

rocking chair

furniture lamp torchiere desk lamp

table end table coffee

table Superordinate Basic Subordinate


More subordinate examples

Granny SmithHatchback

Manx catDessert spooon


Basic level categories

The most inclusive level at which:– There are characteristic patterns of behavioral

interaction– A clear visiual image can be formed

Used for everyday reference


Basic-Level Categories

Brown 1958, 1965, Berlin et al., 1972, 1973Folk biology:

– Unique beginner: plant, animal– Life form: tree, bush, flower– Generic name: pine, oak, maple, elm– Specific name: Ponderosa pine, white pine– Varietal name: Western Ponderosa pine

No overlap between levelsLevel 3 is basic

– Corresponds to genus– Folk biological categories correspond accurately to

scientific biological categories only at the basic level

Slide from Ray Larson and Marc Davis


Evidence Basic Level is Special

People almost exclusively use basic-level names in free-naming tasks

Children learn basic-level concepts sooner than other levels

Basic-level is much more common in adult discourse than names for superordinate categories

Different cultures tend to use the same basic-level categories, at least for living things

Joel Cooper Slide


Prototype effects

Rate the following from 1-7 as examples of vegetables– 1: very good example– 2: good example– 3: fairly good example– 4: moderately good example– 5: fairly poor example– 6: bad example– 7: very bad example/not an example

Turnip, egglant, rhubarbPea, zucchini, parsleyPotato, lemon, tomatoCarrot, cabbage


Goodness of Exemplar tasks: Answer with “Yes” or “No”

All robins are birds All fish can swim Some birds can swim A bat is a bird All birds can fly Some birds are fish An ostrich is a bird All birds are robins

We then measure the time it takes people to answer


Results of these Goodness-of-Exemplar tasks

Order of mention: prototypical member mentioned earlier

Overall frequency: mentioned more frequentlyOrder of acquisition: prototypical members

acquired first by childrenVocabulary learning: is better if definitions of

new words rely on prototypesSpeed of verification: faster for prototypes


What about “bachelor”

An unmarried man Is the pope a bachelor?a newborn male baby?A man who has been living with the same

woman for 40 years, they have three children, share finances?

A single gay man?

Definition of “bachelor” has to be understood with respect to some background frame, in this case the frame of the institution of marriage, of the norms of whatever society we are talking about.


Frames

To understand the meaning of bachelor, or of words like “dessert” or “menu” or Chinese “siu ye”:– You need to have an entire background model of:– How a European/American meal progresses and the

role of sugar in the sequence (for dessert)– What it means to “eat in a restaurant” (for menu)– How a Chinese day progresses and the role of late-

nite meals and who cooks them.

It’s not clear how to represent this knowledge formally.– We saw some of this in the very long definitions in

the Goddard text


“Social division of labor” with meaning: fruit Botantically: (American Heritage dictionary):

– “The ripened ovary or ovaries of a seed-bearing plant, together with accessory parts, containing the seeds and occurring in a wide variety of forms.”

Legally: Nix v. Hedden, 149 U.S. 304 (1893) (is tomato a fruit or a vegetable wrt the Tariff Act of 1883, which taxed imported vegetables but not fruit):– “The court takes judicial notice of the ordinary meaning of all

words in our tongue..Tomatoes are "vegetables," and not "fruit," within the meaning of the Tariff Act …

– …In the common language of the people, whether sellers or consumers of provisions, all these are vegetables which are grown in kitchen gardens, and which, whether eaten cooked or raw, are, like potatoes, carrots, parsnips, turnips, beets, cauliflower, cabbage, celery, and lettuce, usually served at dinner in, with, or after the soup, fish, or meats which constitute the principal part of the repast, and not, like fruits generally, as dessert.


Summary

Word meaning is represented at the level of the word sense Relations between senses

– Two words with same form, different meaning: homonyms– A word with multiple related senses: polysemy– Absolutely synonymy rare, near-synonymy more common– Other sense relations: meronymy, hypernymy.

Classical (Aristotelian) definitions of meaning are based on necessary and sufficient conditions.– Don’t seem to work outside of mathematics

Whatever model we create for explaining word meaning, it must at least deal with these phenomena:– Basic level categories– Prototypes– Family resemblances– Function as an element of meaning

Common versus botanical usage: who gets to decide?

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1 LING 62n Autumn 2008 LINGUIST 62n Language and Food Background Lecture: Word Meaning Oct 2, 2008 Dan Jurafsky