Transcript 32-SemanticsII

Semantics, part 2
December 3, 2012
And Then There Were Three
• Course Evaluations at the end of today’s lecture!
• Semantics/Pragmatics homework still due on
Wednesday
• I will also pass out a final exam review checklist on
Wednesday
• Wednesday: some comments on language preservation
• Friday: an opportunity to ask some review questions
• Semantics homeworks will be graded by Friday
Meaning Review
• Referent: the actual thing in the world an expression picks
out.
• Extension: a set of referents (= a predicate) in some
possible world.
• Sense: what an expression refers to in all possible worlds.
• Truth: a proposition is true if the referent of its subject is
contained in the extension of its predicate.
• Meaning:
• The meaning of a proposition is the set of conditions in
which that proposition is true.
• Truth conditions
Compositionality
• By the way:
The idea that the meaning of a sentence can be
calculated from the meaning(s) of its parts is the
principle of compositionality.
• Consider this sentence:
The President of the United States is a white male.
• Is this true? How do you know?
• How about this sentence:
Santa Claus is a white male.
Types of Sentences
•
Propositions may be distinguished on the basis of the
kinds of worlds in which they may be true.
1. Synthetic propositions may be true or false,
depending on the state of affairs in the world.
2. Analytic propositions are always true, no matter
what the state of the world.
3. Contradictions are always false, no matter what the
state of the world.
•
Quick Write check.
Moving On (Again)
•
There are several different ways to study meaning in
language:
1. Pragmatics
The meaningful use of linguistic expressions in
conversation and discourse.
2. Compositional Semantics
How the meaning of phrases and sentences is built up
from the meanings of individual words.
3. Lexical Semantics
The meaning of individual words, and how they’re
related to one another.
Lexical Semantics
•
Here are two basic meaning relationships that words
can have with one another:
1. Synonymy
•
Two words have the same meaning
•
couch/sofa, groundhog/woodchuck, hide/conceal
•
= real-world extensions are identical
2. Hyponymy
•
one word’s extension is a subset of another word’s
extension
•
poodle/dog, laptop/computer, gas giants/planets
Synonym Schematic
Fido
Marmaduke
Garfield
Rex
Spot
Snoopy
Fifi
Mr. Meowser
Scooby
The Death Star
Lassie
is a dog
is a canine
canines and dogs are
synonyms
Hyponym Schematic
Fido
Marmaduke
Garfield
Rex
Spot
Snoopy
Fifi
Mr. Meowser
Tinkerbell
The Death Star
Lassie
is a dog
is a poodle
poodle is a hyponym
(subset) of dog
Another One
• Antonymy: when words that mean the “opposite” of each
other
• Complementary antonyms:
• Everything in the world is one or the other
• unmarried/married, present/absent, visible/invisible
• Relational antonyms:
• Reflect a symmetrical connection between each other
• give/receive, buy/sell, teacher/pupil
• employer/employee, adviser/advisee
• Scalar antonyms: words form two ends of a scale
• hot/cold, happy/sad, big/small, fast/slow
Homonyms/Homophones
• Homonyms/Homophones are words with:
• same pronunciation
• unrelated meanings
• from Greek: /homo-/ “same” + /onyma/ “name”
• Examples:
• trunk (of an elephant), trunk (chest), trunk (of a tree)
• also: bear, bare
• Homonyms can create ambiguity:
• We saw her duck.
Polysemy
• Polysemy is when one word has several different, but
related meanings.
• From Greek: /poly-/ “many” + /sema/ “signal”
• Examples:
• Mouth of a river ~ mouth of an animal
• A baseball diamond ~ a geometric diamond ~ a
diamond stone
Intersection
• Compositional semantics, continued...
• We have discussed how the referents of nouns and
the extensions of predicates get put together to form a
meaningful proposition.
• Now let’s consider adjectives and nouns in noun phrases.
• Simplest case: pure intersection
• black dogs =
• the set of all dogs
intersected with
• the set of all black things
Pure Intersection Schematic
Marmaduke
Odie
Lassie
Charcoal
Spot
Rex
Darth Vader
Spuds
Oil
dogs
black
dogs
black things
Pure Intersection of Geekery
Semantic Features
• Idea: the meaning of a word can be precisely determined
by the pure intersection of predicates of which it is a
hyponym (subset).
• Example: “square”
[TWO-DIMENSIONAL, FOUR-SIDED, EQUAL-SIDED]
• Example: “bachelor”
[HUMAN, MALE, UNMARRIED]
• The predicate sets form a word’s semantic features
• “hen” and “mare” share the feature [FEMALE]
• “bachelor” and “woman” share the feature [HUMAN]
Verb Features
• The same semantic feature can be expressed by a variety
of different verbs.
• Example: the feature [GO]
• reflects a change in position
• fly, walk, roll, stumble, run, crawl, etc.
• More subtle examples of [GO]:
• give: “John gave Mary an engagement ring.”
John
Mary
ring
• “The boy threw the ball over the fence.”
A Syntax Flashback
• Remember that, in syntax, we learned that different verbs
require specific complement structures.
• For instance, transitive verbs require an object NP in
their verb phrases.
I devoured the sandwich.
I met the Professor.
• Similarly, ditransitive verbs can take two objects in their
verb phrases.
The dog trainer sold me a chew toy.
Larry gave Shelly the textbook.
Syntax/Semantics
• There are sub-features of [GO], which are reflected in
constraints on verb complements in English.
• [BALLISTIC]: a one-time [GO]
V’  V NP NP
• [SUSTAINED]: a continuous [GO]
*V’  V NP NP
• Ballistic Verbs
Sustained Verbs
throw the boy a ball
*push the boy a ball
toss the boy a ball
*pull the boy a ball
kick the boy a ball
*lift the boy a ball
fling the boy a ball
*drag the boy a ball
Role-playing
• The objects of ditransitive verbs can be expressed in two
different syntactic ways:
Larry gave Shelly the textbook.
(NP NP)
Larry gave the textbook to Shelly.
(NP PP)
• Despite the syntactic differences, each noun plays the same
role in both sentences:
Larry: Agent
(the entity performing the action)
Textbook: Theme
(thing being acted upon)
Shelly: Recipient
(being coming into possession
of something)
Thematic Roles
• Verbs have semantic requirements.
• For a sentence to make sense, it has to include nouns
which can play the roles required by the verb.
• give: Agent; Theme; Recipient
Larry gave Shelly the textbook.
Larry gave the textbook to Shelly.
Shelly was given the textbook by Larry.
!Anger gave Shelly the textbook.
Other Thematic Roles
• Experiencer
• = animate being that has a perceptual or mental
experience.
• Ex: Susan heard the music.
• Source
• = the origin of a change.
• Ex: Jan arrived from Detroit.
• Instrument
• = the means used to accomplish an action (not agent)
• Ex: The hammer cracked the window.
Other Thematic Roles
• Goal
• = the end point of a change in location or possession.
• Ex: Chris hitchhiked to Alaska.
• Location
• = the place where an action occurs.
• Ex: Neil Young played a show in Winnipeg.