LINGUIST 62nLanguage and Food Background Lecture: Word Meaning Jan 17, 2008 Dan Jurafsky
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 meanings • Clear 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 bankwas 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 example • While 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 systematic • School, university, hospital • Can 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 • Synonymy • Antonymy • Hypernomy • Hyponomy • Meronomy
Synonyms • Word that have the same meaning in some or all contexts. • filbert / hazelnut • couch / sofa • big / large • automobile / car • vomit / throw up • Water / 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 identical • Still may not preserve the acceptability based on notions of politeness, slang, register, genre, etc. • Example: • Water and H20 • Big/large • Brave/courageous
Synonymy is a relation between senses rather than words • Consider the words big and large • Are 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 up • large lacks this sense
Antonyms • Senses that are opposites with respect to one feature of their meaning • Otherwise, they are very similar! • dark / light • short / long • hot / cold • up / down • in / out • More formally: antonyms can • define 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 of another if the first sense is more specific, denoting a subclass of the other • car is a hyponym of vehicle • dog is a hyponym of animal • mango is a hyponym of fruit • Conversely • vehicle is a hypernym/superordinate of car • animal is a hypernym of dog • fruit is a hypernym of mango
Hypernymy more formally • Extensional: • The class denoted by the superordinate • extensionally 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/dictionary • http://www.cogsci.princeton.edu/cgi-bin/webwn
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 circular • Find 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 conditions • A closed flat figure • Having four sides • All sides are equal in length • 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 conditions • No common properties • Even though each exemplar of games resembles each other • We 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 Smith • Hatchback • Manx cat • Dessert 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, 1973 • Folk 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 levels • Level 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, rhubarb • Pea, zucchini, parsley • Potato, lemon, tomato • Carrot, 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 frequently • Order of acquisition: prototypical members acquired first by children • Vocabulary learning: is better if definitions of new words rely on prototypes • Speed of verification: faster for prototypes
What about “bachelor” • An unmarriedman • 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 • Idea that to understand the meaning of bachelor, or of sentences like • John asked to see the menu • You need to have an entire background model of what it means to “eat in a restaurant” • It’s not clear how to represent this knowledge formally.
“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 • Two words with same form, different meaning: homonyms • A word with multiple related senses: polysemy • Absolutely synonymy is very rare, but near-synonymy is 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 • Basic level categories • Prototypes • Family resemblances • Common versus botanical usage: who gets to decide?