Syntax

Syntax is the study of structure of sentences.

Sentence

Sentence

A sentence expresses a complete meaning. The meaning of every morpheme must be memorized. However, the meaning of every sentence is predictable given the parts.

Principle of Compositionality

The meaning of the whole sentence is the meaning of the parts (syntactic categories) plus how they are combined (syntactic rules).

Link to original

Grammar

Grammar

Mental Grammar

A speaker’s unconscious knowledge of how a language works. A sentence is grammatical in a language if it follows the rules in the mental grammar of that language. A sentence is ungrammatical if it breaks t hose rules: that is, if it is something that people would not say.

Colorless green ideas sleep furiously., * Green sleep colorless furiously ideas.

I have a friend who is always full of ideas, good ideas and bad ideas, fine ideas and crude ideas, old ideas and new ideas. Before putting his new ideas into practice, he usually sleeps over them to let them mature and ripen. However, when he is in a hurry, he sometimes puts his ideas into practice before they are quite ripe, in other words, while they are still green. Some of his green ideas are quite lively and colorful, but not always, some being quite plain and colorless. When he remembers that some of his colorless ideas are still too green to use, he will sleep over them, or let them sleep, as he puts it. But some of those ideas may be mutually conflicting and contradictory, and when they sleep together in the same night they get into furious fights and turn the sleep into a nightmare. Thus my friend often complains that his colorless green ideas sleep furiously.

Prescriptive Grammar

Someone’s ideas about what makes for correct or good writing.

Descriptive Grammar

A description of the rules people actually follow in normal language use.

Link to original

Syntactic Categories

Syntactic Categories

Two words or phrases are in the same syntactic categories if and only if you can interchange them every sentence without making the sentence ungrammatical.

Common Syntactic Categories and Phrases

• Noun Phrases (NP):
  • Take determiners (the, a, his, few, some, most, this) as specifiers.
  • Modified by AdjPs, PPs, AdvPs, and NPs.
  • May consist of a single pronoun (Pro).
• Verb Phrases (VP):
  • Take NP as complements, depending on the transitivity:
    • Intransitive: takes only a subject (sleeps, eats).
    • Transitive: takes a subject and direct object (hit, smokes).
    • Ditransitive: takes a subject, direct object and indirect object (gave).
  • Modified by AdvP, PP, and NP of time.
• Adjective phrases (AdjP): Take qualifiers (very, quite, a little) as specifiers answering “how.”
• Prepositional Phrases (PP): Take NP as complement (into the room), qualifiers as specifiers (straight onto the bed).
• Adverb Phrases (AdvP): Take qualifiers (very, too) as specifiers.
• Conjunctions (Conj): Combines two phrases of the same type (XP + XP -> XP). (e.g., for, and, nor, but, or, yet, although)
• Determiners (Det): Articles (a, the), possessives (my, his), quantifiers (few, some, every), demonstratives (this, those).
• Complementizer Phrases (CP): Complementizer C (that, if, whether) takes a TP complement.
  • VPs can take CPs as object complements (know that you are watching), or CPs can serve as subjects.

Link to original

Syntactic Constraints

Co-Occurence Constraints

If you have one word somewhere in a sentence, you must also have another word somewhere else in the sentence.

Sally hasn't read the book., * Sally hasn't read the., * Sally hasn't read the this book., * Sally hasn't read three book.

Link to original

Word Order Constraints

Words must be placed in a certain order for a sentence to be grammatical.

Sally hasn't read the book., * Sally hasn't read book the., Sally saw the book., * Saw Sally the book., * Sally the book saw.

Link to original

Syntactic Rules

Syntactic Rules

Syntactic Rules

Syntactic rule states what words can form a syntactic category and in what order.

NP(the cat) -> Det(the) N(cat)

Lexical Entity

Lexical Entity

A rule that spells out individual words in a category.

N -> cat, mouse, dog, person

Link to original

Rule Types

• Head rules (XP -> ... X ...): Expand a phrase into a head plus complements/specifiers (e.g., VP -> V NP, PP -> P NP).
• Adjunction rules (X -> ... X ...): Expand a category into itself plus optional adjuncts (e.g., VP -> VP Adv, N -> Adj N).
• Exocentric rules: Expand a category into other categories of different types (e.g., TP -> NP T' or S -> NP VP).# Syntactic Rule Examples
• Recursive rule: a syntactic rule can be recursive. (e.g., N -> Adj N)

Syntactic Rule Examples

• S: S -> NP VP
• VP: VP -> V, VP -> TV NP, VP -> DTV NP NP, VP -> SV S, VP -> VP Adv, VP -> VP PP
• NP: NP -> Det N, NP -> PropN
• N: N -> Adj N, N -> N PP
• PP: PP -> P NP

General Phrase Structure Principles

• Head (X): Core element that projects into a phrase of the same type (XP).
• Specifiers: Provide additional information about the head. (e.g., Det in NP)
• Complements: Required by heads to complete the phrase.
• Modifiers: Optional elements. Can be freely reordered relative to each other.

Sentence as Tense Phrase

A sentence combines a subject and a predicate incorporating tense via a Tense Phrase (TP).

• Head (T): Tense ([+past] or [-past]) or Modals (can, will, must). Modals take the place of tense under T, making the following verb non-tensed.
• Specifier: Subject NP.
• Complement: Predicate VP.

Auxiliaries (AuxP)

Function as helping verbs between TP and VP.

Start with a sentence "He would have left".
TP
├─ NP
│  └─ N: He
├─ T: would
└─ AuxP
   ├─ Aux: have
   └─ VP
      └─ V: left

• Progressive auxiliary: continuation of an event. e.g., is V-ing, was V-ing
• Perfective auxiliary: completion of an event. e.g., had V-ed, have V-ed
• Passive auxiliary: focus on the object of the sentence. e.g., is V-ed, are V-ed

Generation

Generation (Syntax)

Start with S and randomly choose which rules to follow until you have generated a sentence.

Start with "S"
S
├─ NP
│  ├─ Det: that
│  └─ N: person
└─ VP
   ├─ VP
   │  └─ V: slept
   └─ Adv: badly

Link to original

Parsing

Parsing (Syntax)

Start with a sentence and figure out how it could have been generated by the rules.

Start with a sentence "Sally thought the dog chased the furry cat".
S
├─ NP
│  └─ PropN: Sally
└─ VP
   ├─ SV: thought
   └─ S
      ├─ NP
      │  ├─ Det: the
      │  └─ N: dog
      └─ VP
         ├─ TV: chased
         └─ NP
            ├─ Det: the
            └─ N
               ├─ Adj: furry
               └─ N: cat

Process of Parsing a Sentence

1. Label the categories for all the individual words.
2. Find a sequence of categories that matches the right-hand side of a rule.
3. Draw a tree with the left-hand side of the rule on top.
4. Repeat until you have a single tree that covers all the words in the sentence.

Link to original

Link to original

Syntactic Ambiguity

Syntactic Ambiguity

Lexical Ambiguity

A word belongs to multiple different Syntactic Categories.

TV -> love, N -> love

Structural Ambiguity

The same sequence of words has multiple different parse trees.

Mary saw (the mouse (in the house)) and Mary (saw (the mouse) (in the house))

Link to original

Syntactic Analysis

Syntactic Analysis

The goal of syntactic analysis is to write down syntactic rules that generates all and only the grammatical sentences in a language.

Link to original