Syntax, FILOLOGIA ANGIELSKA, Linguistics
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P. Schlenker -
Ling 1
- Introduction to the Study of Language, UCLA
Introduction to Language - Lecture Notes 4A
Sentence Structure I: Syntactic Trees
☞
Goal:
What is the structure of sentences? A natural assumption is that sentences are mere strings of
words, with no special structure (this is what we call 'Hypothesis 1'). This assumption is incorrect, however.
We show that sentences have more structure than meets the eye: they are organized into subgroups of words,
which are called 'constituents'. Constituents have a tree-like structure, which has lead linguists to represent
sentences as syntactic trees (this is what we call 'Hypothesis 2'). The crucial argument in favor of Hypothesis
2 and against Hypothesis 1 stems from certain
tests
(called 'constituency tests'), in which a group of words is
targeted by a certain operation to yield another sentence. If the operation succeeds, and yields a grammatical
sentence, the group of words in question behaves as a natural unit, and is likely to be a 'constituent'. For
instance in
Mary will meet the President
the words
the President
can be moved as a unit to the beginning of
the sentence, yielding
The President, Mary will meet
, which is grammatical. We conclude that
the President
is a constituent. By contrast, if we attempt to move to the beginning of the sentence the words
meet the
, the
result is ungrammatical:
*Meet the Mary will President.
This suggests that
meet the
is not a constituent. With
this background in mind, we give an account of
structural ambiguities
, i.e. cases in which a given string of
words can be organized into two distinct trees, with different meanings.
1
Sentences Have a Tree Structure
1.1
Two Hypotheses: Sentences have a flat structure vs. Sentences have a tree-like structure
Let us consider first two very simple sentences, as in (1)a-b:
(1)
a. Mary will meet the President
b. Your friend will meet the President
The simplest assumption -one which will turn out to be incorrect- is that this sentence is a mere juxtaposition
of words. According to this hypothesis the sentence has a 'flat' structure, which does not give any information
besides the fact that certain words are contiguous to certain other words:
Hypothesis 1: Sentences are just strings of words and thus have a 'flat' structure'.
(2)
Mary
will
meet
the
President
1
P. Schlenker -
Ling 1
- Introduction to the Study of Language, UCLA
(3)
Your
friend
will
meet
the
President
Already long ago, however, linguists came to the conclusion that this initial hypothesis is incorrect, and that
in fact sentences have a 'tree-like' structure. Words are grouped together into sub-trees, which in turn are
grouped into larger sub-trees, etc. This view is illustrated below, without justification (we motivate the
particular tree structure we have posited in the next section):
Hypothesis 2: Sentences have a tree-like structure: words are organized into constituents (=sub-trees)
(4)
Mary
will
meet
the
President
(5)
will
Your
friend meet
the
President
Let us say that two words or groups of words 'form a constituent' if there is a sub-tree that contains them and
nothing else (we could have said just as well that they 'form a sub-tree', since a constituent is nothing but a
sub-tree; linguists tend to prefer the word 'constituent', however). We can now make an important
observation about trees:
Two words or groups of words that 'form a constituent' are contiguous. But the converse is not true:
some words or groups of words which are contiguous do not form a constituent.
For this reason a tree-like structure provides strictly more information than a 'flat' structure.
To be concrete, consider some examples:
2
P. Schlenker -
Ling 1
- Introduction to the Study of Language, UCLA
-In (4), the words
the
and
President
are contiguous and form a constituent. But
meet
and
the
, although they
are contiguous, do not form a constituent (there is no sub-tree that contains them and nothing else; in fact the
smallest sub-tree that contains them also contains the word
President
).
-In (4),
will
and
meet
are contiguous, but they do not form a constituent; the smallest sub-tree that contains
both words is
will meet the President,
which also contains additional words (=
the President
). Hence there is
no sub-tree that contains
will
and
meet
and nothing else. By contrast,
meet
and the constituent
the President
form a constituent, and are of course contiguous as well (since whenever two words or groups of words form
a constituent, they are contiguous).
-In (5),
friend
and
will
are contiguous but do not form a constituent. By contrast,
your
and
friend
form a
constituent, and they are of course contiguous (since whenever two words or groups of words form a
constituent, they are contiguous).
Note:
In traditional grammar, the sub-tree (=constituent) that comes to the immediate left of
will
is called the
subject
of the sentence. The sub-tree (=constituent) that comes to the immediate right of
meet
is often called
the
object,
or the
complement
of the verb
meet.
While the terminology used in modern linguistics is
sometimes different, these are essential notions, which will be discussed in somewhat greater detail later in
the course.
Terminology:
It will be useful in what follows to have some terminology to talk about trees and sub-trees.
The points that are joined by segments in a tree are called
nodes.
If a node N' belongs to a sub-tree whose
highest node is N, we say that N
dominates
N'. If N dominates N' and there are no intermediate nodes
between N and N', we say that N is the
mother
of N', and that N' is a
daughter
of N. If N is the mother of N
1
and N
2
, then N
1
and N
2
are
sisters
. (For future reference, we note that a 'branching node' is a node that has at
least 2 daughters; a node that has no daughter at all is called a 'terminal node'; and a node that has 1 daughter
is normally called 'non-branching).
1.2
Arguing for a tree structure: constituency tests
Why should we posit that sentences have a tree-like structure? Because certain groups of contiguous
words behave a natural units - for instance they may stand lone, be moved as a unit, be deleted as a unit, or
be replaced by a pronominal form. Other groups of contiguous words lack these properties, and appear not to
be natural units. The tree structure recapitulates the result of these observations, to which we now come.
Note:
In each of the following, we put brackets around the words that appear to behave as a natural unit
(=as a constituent = as a sub-tree). Note that the information encoded in a tree can also be represented with
brackets (=put brackets around each group of words that form a sub-tree).
♦
Constituency Test 1: Ability to stand alone
(6)
a. Mary will meet [the President]
b. Who will Mary meet?
-The President
☞
the
and
President
can stand alone as a unit; this suggests that they form a constituent.
3
P. Schlenker -
Ling 1
- Introduction to the Study of Language, UCLA
(7)
a. Mary will [meet the President]
b. What will Mary do?
-Meet the President
☞
meet
and
the President
can stand alone as a unit; this suggests that they form a constituent.
(8)
a. [Your friend] will meet the President
b. Who will meet the President?
-Your friend
☞
your
and
friend
can stand alone as a unit; this suggests that they form a constituent.
Note, by contrast, that
will meet
,
meet the
or
friend will
cannot stand alone as units:
(9)
a. *will meet
b. *meet the
c. *friend will
☞
If a group of words can stand alone, they form a constituent
♦
Constituency Test 2: Ability to move as a unit
(10)
a. Mary will meet [the President]
b. [The President], Mary will meet
☞
the
and
President
can be moved as a unit to the beginning of the sentence; this suggests that they form a
constituent.
(11)
a. Mary will [meet [the President]]
b. [Meet the President], Mary will
e.g. in the following context:
John told you that Mary will meet the President, and
[meet the President], Mary (certainly) will.
☞
meet
and
the President
can be moved as a unit to the beginning of the sentence; this suggests that they
form a constituent.
[In order to apply the test to
your friend,
we must not only move it to the beginning of the sentence, but also
replace it with a pronoun:
(12)
a. [Your friend] will meet the President
b. [Your friend], she will meet the President.]
Note, by contrast, that other movements are excluded:
4
P. Schlenker -
Ling 1
- Introduction to the Study of Language, UCLA
(13)
a. *Will meet, Mary the President
b. *Meet the, Mary President
b. *Friend will, your the President
☞
If a group of words can be moved as a unit, they form a constituent
♦
Test 3: Replacement by a pronoun
The reasoning we made with respect to Test 1 and Test 2 can be replicated with our 3
rd
tests, which consists
in the possibility to replace a group of words by a pronoun that, intuitively, 'means the same thing' as the
words it replaces.
(14)
a. Mary will meet [the President]
b. Mary will meet
him
(15)
a. Mary will [meet the President]
b. -No, she won’t do
it
(16)
a. [Your friend] will meet the President
b.
She
will meet the President
☞
If a group of words can be replaced by a pronoun, they form a constituent.
Constituency Tests
1.
If a group of words can stand alone, they form a constituent.
2.
If a group of words can be moved as a unit, they form a constituent
3.
If a group of words can be replaced by a pronoun, they form a constituent
.
Important Note:
A group of words may be a constituent
without
satisfying some of the tests.
The trees in (4) and (5) recapitulate the result of our observations:
[the President] is a constituent
[meet [the President]] is a constituent
[your friend] is a constituent.
(Note that each of the groups of words that we have put inside brackets form a sub-tree in (4) and (5))
We will further assume without argument that [will [meet [the President]]] is also a constituent.
5
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