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Syntax 2
Ling400
Phrasal Categories
• A group of words that behave like a unit
• A phrase is used as a constituent of a
sentence.
• English is claimed to have such phrasal
categories as NP (noun phrase), VP
(verb phrase), PP (prepositional
phrase), AP (adjective phrase), etc.
Noun phrases
• Can occur as the subject or object of a sentence.
• Bare nouns: proper nouns, plural and mass nouns
such as Lynn, Chicago, plants, snow
• Determiner + Noun (D+N) such as a train, my
brother, the island, some bandits
• (D) + adjective + N such as my best friend, an early
ferry, a big fat bone, white snow
• (D) + N + PP as the captain of a ship, the flowers on
the green table
Noun phrases (examples)
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a train
Chicago
Lynn
Flora
Hudson St.
the Beatles
some bandits
another state
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An engineer
Plants
An early ferry
My best friend
Mrs. Jones
A big bone
Snow
Animals
Other phrases
• VP: clearly sees some flowers, quietly
put paper in the printer
• AP: very pretty, extremely dependent on
coffee
• PP: on a green table, high over the door
Why do we need phrases?
• The idea is that by using phrasal
categories, we can describe the rules of
syntax in a succinct manner.
• What would happen if we didn’t use
phrasal categories to describe rules?
• There would be no structural ambiguity
otherwise.
Ambiguity (three types)
• Lexical ambiguity (e.g. bank)
• Structural ambiguity
E.g. We need more intelligent
administrators.
• “Scope ambiguity” (a tough one)
E.g. Every boy likes some girl.
(More) Ambiguity Examples
• My son has grown another foot. [lexical]
Will he need to buy his shoes in threes?
• Mary had a little lamb. [lexical]
Was the midwife surprised?
• Sisters reunited after 18 years in checkout
line at supermarket. [strcutural]
Were they in line for 18 years?
What rules would we need?
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John slept on the couch.
John likes Bill.
The man loves music.
The girl likes the boy.
The architect built that tall building in
1995.
• …… (endless)
Rules without phrasal
categories
S Name V P Det N
S  Name V Name
S  Det N V N
S  Det N V Det N
S  Det N V Det Adj N P Name
…. (endless)
Rules with phrasal categories
S NP VP
NP  Name
NP  Det N
VP  V (NP)
VP  VP PP
PP  P NP
(finite and more manageable)
Structural ambiguity again
The price includes soup or salad and french fries
Give an unambiguous paraphrase.
Phrase Structure Rules
(slightly augmented)
S NP VP
NP  N
NP  Det (AdjP) N
VP  V (NP)
VP  VP PP
PP  P NP
NP  NP Conj NP
VP  V (that) S
VP  V (that) S
() indicates optionality
Structural ambiguity
The price includes soup or salad and french fries
NP
NP
NP
NP
NP
Nm
soup
Conj
Nm
or
salad
Conj
and
Npl
french fries
Structural ambiguity
The price includes soup or salad and french fries
NP
NP
NP
NP
NP
N
Conj
N
soup
or
salad
Conj
and
N
french fries
PS rules account for the
ambiguity
• We have seen that both structures can
be produced by the same set of phrase
structure rules.
• A set of rules without phrasal categories
cannot account for structural ambiguity.
PS rules have a
“recursive” nature
• Many PS rules have a phrasal categories on
the right side of the arrow.
• By combining such rules, we can fine a rule
or set of rules that apply “recursively”. That is,
those that can be re-applied for any number
of times. This results in a sentence that
“never comes to an end”.
• E.g. NP --> NP Conj NP
Wh Questions
• Sometimes, some expressions seem to occur
in “the wrong place”:
I bought a book.
*I bought.
*What did you buy a book?
What did you buy?
(makes sense if what is the “direct object” that
is moved to the front of S.)
The main point
• A significant generalization is lost if we merely depend
upon PS-rules to generate English sentences.
• Try generating the following sentences only with PSrules.
John can eat fish.
What can John eat?
*What can John eat fish?
*What will John disappear?
John will disappear.
Wh-movement transformation
John can eat fish.
can John eat what?
*can John eat fish what ?
*will John disappear what?
John will disappear.
• what is generated in a regular NP
position and moves to the front of the
sentence.
WH movement
S
NP
Mary Aux
has
V
eaten
VP
NP
what
WH movement
S
NP
What
Aux
has
NP Aux
Mary [has]
V
eaten
VP
NP
[what]
Subj.-Aux. inversion
John can eat fish.
John can eat what?
*John can eat fish what ?
*John will disappear what?
John will disappear.
• auxiliary verbs are generated between the
subject NP and the main verb.
• subj and aux then switch positions in whquestions.
Wh-movement+Subj-Aux inversion
S
WH
What
Aux
has
NP
Mary Aux
[has]
VP
V
eaten
NP
[what]
Two rules or just one?
Just Subj-Aux inversion
(1) Can Mary join us tomorrow?
Just Wh-movement
(2) I know who Bill met.