Transcript 20-SyntaxII

Syntax II
“I really do not know that anything has ever been more
exciting than diagramming sentences.”
--Gertrude Stein
Quick Review
• Syntax: the study of how words are put together to form
sentences and phrases.
• These rules operate on lexical categories…
• independently of the meaning of the words.
• Lexical categories can be defined by:
• the syntactic distribution of words
• the types of inflectional affixes which may attach to
them
• Lexical categories (noun, verb, adjective, preposition,
etc.) were used to make the old game “Mad Libs” work.
The Last Quick Write
• Mad Libs!
• The following sentence is both grammatical and
(somewhat) sensible:
Colorless Green Libs?
• These sentences are grammatical but don’t make that
much sense:
Bad Libs.
• The following sentences are not grammatical.
Bad Libs.
• The following sentences are not grammatical.
Artsy Libs.
• Some of you were quite enthusiastic about the exercise.
How does this work?
• We know that words of different lexical categories have
to fit together with the words in their environment to
make a sentence grammatical.
• A first hypothesis--the rules for putting sentences
together string one word category after another:
S  Det N V Det N
( = “may consist of”)
The child found a puppy.
S  Det A N V P Det N
The slithy toves gimbled in the wabe.
• These syntactic rules capture patterns of words.
Important Data
•
What’s going on in these sentences?
1. We need more intelligent leaders.
2. I like green eggs and ham.
3. The police shot the terrorists with rifles.
•
 Syntax also puts words together in units that are
smaller than sentences.
•
•
These units are called phrases.
Same string of words, more than one interpretation =
•
more than one phrase structure
•
structural ambiguity
Ambiguity (again)
• In order to represent phrase structure, we will use tree
diagrams.
more intelligent leaders
more intelligent leaders
Phrases
•
The nodes in a syntactic tree above the word level
represent phrases.
•
•
phrase = string of words that function as a unit
Basic phrase types:
1. Noun Phrases (NP): [intelligent leaders]
2. Verb Phrases (VP): [shoot terrorists]
3. Prepositional Phrases (PP): [with rifles]
4. Adjective Phrases (AP): [more intelligent]
Phrase Phacts
• Every phrase has to have at least one constituent
• This constituent is called the head of the phrase.
• The head determines the phrase’s function, behavior and
category.
• For example, noun phrases have to consist of at least one
noun.
Robin
the book
a picture of Robin
a picture of the unicorn
that weird picture of Bob’s unicorn
In General
• There’s a pattern to how these things work:
• Noun phrases (NPs) are headed by nouns
• NP  N
• Verb phrases (VPs) are headed by verbs
• VP  V
• Prepositional phrases (PPs) are headed by
prepositions
• PP  P
• Adjective phrases (APs) are headed by adjectives
• AP  A
• Basic Phrase Structure Rule: XP  X
More About Phrases
•
Beyond the heads, phrases can be expanded with
specifiers and complements.
•
Specifiers precede the head of the phrase;
•
•
they pick out a particular version of the head.
Examples:
1. this book
(Determiner specifying noun)
2. very late
(Degree word specifying adjective)
3. often forgets
(Adverb specifying verb)
4. almost in
(Degree word specifying preposition)
Complements
•
Complements always follow the head of the phrase…
•
And provide more information about that head.
1. this book about unicorns
•
PP complement of the head of the NP.
2. very late to class
•
PP complement of the head of the AP.
3. often forgets his hat
•
NP complement of the head of the VP.
4. almost in the basket
•
NP complement of the head of the PP.
X-Bar Theory
• Together, heads and their complements form a phrasal
structure known X’ (“X-bar”).
• Here’s the way phrases (of all kinds) normally break
down:
XP
X’
(Specifier)
• note: heads are the
only obligatory element
in the phrase
• optional stuff is in
parentheses
X
Head
(Complement)
Tests for Phrase Structure
•
There are some tests you can use to figure out if a
group of words constitutes a phrase.
1. Substitution
•
Phrases (and only phrases) can be substituted for
by shorter expressions.
•
Ex: Pronouns can be substitutes for NPs.
•
 The coach wanted a picture of the book.
•
She wanted a picture of the book. (= the coach)
•
The coach wanted it. (= a picture of the book)
•
The coach wanted a picture of it. (= the book)
Tests for Phrase Structure
•
VPs can be substituted with the phrase “do so”.
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PPs can be substituted with “there”.
•
•
Ex: The coach dropped the ball, and the professor
did so, as well. (= dropped the ball)
The children waited at the corner, and we waited
there, too. (= at the corner)
Substitutions do not work for non-constituents (or the
wrong constituents):
•
*The coach dropped the ball, and the did so, too.
•
*The children waited at the corner, and we waited at
there, too.
•
*The coach dropped the it.
Tests for Phrase Structure
2. Movement: sometimes, constituents can be moved to
another part of the sentence.
•
NP movement: He hated the Jedi Knights. 
•
•
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Bad examples:
•
*Jedi Knights, he hated the.
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*The Jedi, he hated Knights.
VP movement:
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•
The Jedi Knights, he hated.
Hate the Jedi Knights, he did.
PP movement: We ran up the hill. 
•
Up the hill, we ran.
Tests for Phrase Structure
3. Coordination
•
•
Conjunctions like {and, but, or} coordinate phrases
of the same type.
NP-coordination:
•
I like [romantic sunsets] and [long walks on the
beach].
•
PP: We went [over the river] and [through the woods].
•
VP: They want to [eat pizza] or [play video games].
•
AP: The blizzard was [very intense] but [surprisingly
short].
Tests for Phrase Structure
3. Coordination
•
Conjunctions like {and, but, or} coordinate phrases
of the same type.
•
Coordination of unlike phrases can sound quite bad:
•
NP + AP: *I like [romantic sunsets] and [surprisingly
short].
•
PP + VP: *We went [over the river] and [play video
games].
•
VP + NP: *They want to [eat pizza] or [long walks on
the beach].
•
AP + PP: *The blizzard was [very intense] but
[through the woods].
Example Tree
NP
Det
N’
the
N
book
How about: “a picture of the book?”
NP
Det
N’
a
N
PP
picture
P
NP
of
Det
N’
the
N
book
More Example Trees
• Let’s draw trees for the following phrases:
• VP: often forgets his hat
• PP: almost in the basket
• AP: very late to class
VP
Adv
V’
often V
forgets
A VP Example
NP
Det
N’
his
N
hat
AP
Deg
A’
very
A
PP
late
P
NP
to
N’
An AP Example
N
class
Check This Out
1. A phrase structure rule for NPs looks like:
•
NP  Det N’
2. And a PP can be a complement of a head noun:
•
N’  N PP
3. And an NP can be a complement of a prepositional
phrase:
•
•
PP  (Deg) P’
•
P’  P NP
Where can this combination of rules take us?
Whoa, Nellie
• There is a possibility for infinite recursion.
• NP  Det N PP
• NP  Det N P NP
• NP  Det N P Det N PP
• NP  Det N P Det N P NP
• NP  Det N P Det N P Det N PP, etc.
• Example: the book from the library in the city near the
airport beside the apartment complex with the
playground of the children from the school behind the
train tracks...
• The fact that our grammar can generate phrases like
this is why we need to know patterns of patterns.