Syntax – Week 3, Lecture 2
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Phrase Structure Grammar Cont…
Today:
1. Extending our PSR’s further
2. Phrase Structure Trees: terminology and rationale
3. Ambiguity
4. Heads and dependency relations (incl. adjuncts vs. complements)
1. Extending our PSR’s for English
1. Ditransitive Verbs
We touched upon the fact that some verbs (such as give, cook) can be
followed by two NP’s:
Mary [VP gave [NP the horse] [NP some hay] ]
We can update our VP rule accordingly:
VP → V {
(NP)(NP)
(AdjP)
} (PP*)
2. Phrasal Verbs
We argued at length that the particle
up in the following sentence is not
part of a PP: “Mary rang up her
mother.” We will account for particles
by including a new, optional rule for
verbs:
V → V P
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Where P here is a particle. Note that in more advanced grammars of
English, this rule would be revised.
Be careful: V → V P means that a verb can be made up of a verb plus
particle (the ‘P’ here doesn’t mean ‘phrase’ as in ‘verb phrase’, nor does it
mean ‘preposition).
Also note: this rule is optional, i.e., not all verbs have to ‘rewrite’ as a verb
plus a particle. We don’t use brackets here because we’re not identifying
a particular element within a rule as optional, rather, the whole rule is
optional (i.e. does not always have to apply).
3. Adverbial Phrases
AdvP’s are headed by an adverb:
She ran quickly
She ran very quickly
*She ran very
How did she run? Very quickly
AdvP → (Adv) Adv
Updated PSR’s
S → (Adv) NP VP
VP → V {
(NP)(NP)
(AdjP)
} (PP*)
V → V P
(Optional rule for verb-particle
constructions like “ring up”)
NP → {
Dtv (AdjP*) N (PP*)
PN
PRO
}
AdjP → (Adv)Adj
AdvP → (Adv) Adv
PP → P NP
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2. Phrase Structure Trees: terminology and rationale
2.1 Some basic terminology
A tree structure is made of nodes and dominance relations represented as
lines:
NP
Dtv N
NP, Dtv and N are all nodes of the tree. The dominance relations are
shown by the lines between the nodes. Note: dominance relations are not
allowed to cross. Nodes can be of two types:
Terminal Nodes: Nodes which have no children (e.g., Dtv, N above)
Nonterminal Nodes: Nodes with children (e.g., NP above)
● The NP is the mother to two children. The children are sisters.
● Each node has a label (e.g., N, V, VP etc.)
● Each tree has a root – this is the top node.
PSR’s and Trees are related to each other:
NP → Dtv N NP
Dtv N
Linear Precedence: The left-to-right order of the nodes is called linear
precedence. This order is important – for example, it captures the fact
that prepositions go before NP’s in English, not after.
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The nodes represent constituents –
either word level (terminal nodes)
or phrase level constituents
(nonterminal nodes).
S
NP VP
N V NP
clowns terrify PRO
him
In the tree structure above, clowns is a terminal node. However, clowns
can also be seen as the only word in the subject NP. In this sense, people
refer to clowns as both a noun, and a noun phrase. Note though, we are
actually referring to different nodes.
2.2 Single Noun NPs – a bit more.
People are often confused a word apparently being both a noun and noun
phrase. Let’s sort this out. To do this, we note that a pronoun (such as
them) must substitute with a NP, not a N:
1. The child fears [The old gods]NP
Note that “them” can substitute with “the old gods”, but not gods.
2. The child fears them. [them = the old gods]
3. *The child fears the old them. [them can’t be gods]
Evidence for this is overwhelming:
*The tall she walked down the street.
*The woman saw those you.
Now consider (4):
4a. The child fears gods.
4b. The child fears them.
We already know that “them” will not substitute for “gods”, but it will
swap with a NP. So there simply must be a NP following fears:
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By using clearer terminology, we can see what’s
happening. NP1 has a job – it is functioning as
the object to fears. The noun “gods” is
functioning as head of NP1.
2.3 Rationale for PST’s (Phrase Structure Trees)
A PST gives us an explicit description of the syntax of a sentence with the
following structural/configurational & categorical information:
● the minimal lexical units (words or morphemes) of the sentence
● their linear order
● the hierarchical constituent structure of the sentence
● the syntactic category of both lexical and phrasal units
● relationships between ‘families’ of phrasal units (e.g., N, NP)
In other words, we don’t draw trees just as a matter of convention – a
tree makes a claim about the structure of a phrase or sentence. An
analogy may be made with the structure of an organisation like a
university:
E.g. the tree above makes the claim that SOLL (the School of Languages
and Linguistics) is a part of the Arts Faculty, which in turn is part of the
university. Phrase Structure Trees make the same kind of claims.
(Note: one difference is that linear order is important in PST’s, but
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generally unimportant in other kinds of tree diagrams like those
representing the structure of a university or company.)
3. Ambiguity
3.1 Types of ambiguity
Three types:
Lexical – occurs when a word has more than one meaning.
● I drove the car into the bank.
● I prepared the poison for the judge.
Structural – occurs when a phrase or word can be placed in more
than one place in a tree.
● The [tall bishop]’s hat
● The tall [bishop’s hat]
Scope Ambiguity
There exists another type of ambiguity which involves the interaction
of quantifiers. Quantifiers are words like every, each, no etc. When
more than one is used in a sentence, ambiguities can arise:
Every student read one book last semester.
Two readings:
● Strong Reading: There is one book (Kroeger say), and every
student read it.
● Weak Reading: All the students have read one (or more) books,
but not one book in particular.
Note that whatever reading is inferred from the sentence above, the
tree structure remains unchanged.
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We are going to be interested only in structural ambiguity in this course.
Structural Ambiguity Exercise
Draw the tree structures for:
She caught the man in her pyjamas.
How to approach the solution
When trying to draw the tree structure for a new sentence:
● Knowing where the verb is for the sentence makes it easier to split
the sentence up into constituents.
● If you can find the valency of the verb (i.e., is the verb a copula,
intransitive, transitive or ditransitive verb) – you can predict what
phrases come after the verb.
● The parts of speech for each word should be identified – this helps
identify potential phrases.
● Identify any easy phrases such as NP’s and PP’s.
● Be familiar with the PSR’s. For example, knowing where your verb is
and knowing the rule S–> NP VP makes drawing the tree much
easier.
Prediction:
Which of (a) and/or (b) is ambiguous – can we make a prediction about
the ambiguity of (c) below?
a. The captain saw the sailor with a telescope
b. The captain saw the sailor by chance
c. The captain saw the sailor by chance with a telescope
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4. Heads and Dependency Relations
Phrasal level mother nodes correspond with the category of their head
daughter:
e.g. head of NP is N, head of VP is V, …
Heads determine the category of the mother. Heads are normally
obligatory, whereas the head’s sisters are often optional:
red – (very) red
slowly – (very) slowly
ran – ran (to the shop)
Semantically, the head of a phrase determines what sort of entity,
property or event the phrase as a whole refers to or describes. The other
elements in the phrase provide additional information about the head –
they specify the extent or possible range of application of the head.
Sisters of a head are often called dependents – this is a very important
term. Dependents are either complements or modifiers/adjuncts:
XP
ZP(sister) head:X YP(sister)
XP has three daughters: ZP, YP and the head (X). These three daughters
are all sisters to each other. Both ZP and YP are called dependents of the
head, and they must be either adjuncts/modifiers or complements to the
head.
(Note: in this example, the head is in the middle, but it won’t always be
like that.)
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What is the difference between an adjunct and a complement?
The distinction between complements and adjuncts is subtle and forms a
continuum between those dependents which are wholly complements
and those which are wholly adjuncts – with a large fuzzy area in the
middle.
Basically, if the head of a phrase says something specific about the type of
dependent it is associated with, that dependent is a complement –
otherwise the dependent is an adjunct. For example, consider “chew” and
“build” below:
Here, “chew” tells us that there must be something which can fit inside a
mouth doing the chewing – so “the biscuit” above is a complement to the
V chew. However, chew does not limit the manner of the chewing event,
and so the PP “with gusto” is an adjunct. Similarly for “build” – this verb
requires a thing to be built, and so “the crooked house” is a complement:
However, the N “house” is the head of a NP and this N also has a dependent
(i.e., the AdjP “crooked” to which it is a sister). The meaning of the noun
“house” does not require that people be told about the style of the house
(compare house and crooked with chew and biscuit) and so the AdjP
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“crooked” is an adjunct to the head N house.
Complements
● required in some sense by their heads
● if omitted, still ‘understood’
● complements are subcategorised for by the head (i.e., the head
determines if you get a complement, how many and what kind)
Examples:
Jill gave the child a book.
? Jill gave
? Jill gave a book
Note that neither NP can be easily omitted. So, these are complements.
Contrast with eat below:
I ate some food at noon
I ate some food.
I ate at noon.
I ate.
The food NP can be readily omitted in English – but it is still understood
that I ate something. So, the NP here is a complement but the PP is an
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adjunct.
Adjuncts/modifiers
● not required in the same sense
● adjuncts are always optional
Examples:
The tall child.
I left hurriedly.
The students with good haircuts.
Jill gave the child a book on Monday
Exercise: are the underlined phrases complements or adjuncts?
● The student of linguistics
● The table in the corner
● The chair of the department
NP
Dtv N PP
the student of linguistics
the table in the corner
the chair of the department
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The dependency relations between heads and their complements explain:
● Restrictions imposed by heads on the number of its sisters
(subcategorisation)
● Restrictions imposed by heads on the semantic nature of its sisters
(selectional restrictions)
● Restrictions imposed by heads on the case of its sisters
● Agreement between heads & dependents
● Word order constraints on heads and their dependents