Grammar

Linguistics Essentials


Instructor: Rada Mihalcea

Note: most of the material in this slide set was adapted from an NLP course taught by J. Hajic at Johns Hopkins University


Levels of formal description
Linguistic categories
Words, phrases, sentences
The Description of Language
Language = Words and Rules
 Dictionary (vocabulary) + Grammar

Dictionary
set of words defined in the language
open (dynamic)
Traditional
paper based
Electronic
machine readable dictionaries; can be obtained from paper-based

Grammar
set of rules which describe what is allowable in a language
Classic Grammars
meant for humans who know the language
definitions and rules are mainly supported by examples
no (or almost no) formal description tools; cannot be programmed
Explicit Grammar (CFG, Dependency Grammars, Link Grammars,...)
formal description
can be programmed & tested on data (texts)
Levels of (Formal) Description
6 basic levels (more or less explicitly present in most theories):
and beyond (pragmatics/logic/...)

meaning (semantics)

(surface) syntax

morphology

phonology

phonetics/orthography

Each level has an input and output representation
output from one level is the input to the next (upper) level
sometimes levels might be skipped (merged) or split
Phonetics/Orthography
Input:
acoustic signal (phonetics) / text (orthography)

Output:
phonetic alphabet (phonetics) / text (orthography)

Deals with:
Phonetics:
consonant & vowel (& others) formation in the vocal tract
classification of consonants, vowels, ... in relation to frequencies, shape & position of the tongue and various muscles
intonation
Orthography: normalization, punctuation, etc.
Phonology
Input:
sequence of phones/sounds (in a phonetic alphabet); or “normalized” text (sequence of (surface) letters in one language’s alphabet) [NB: phones vs. phonemes]

Output:
sequence of phonemes (~ (lexical) letters; in an abstract alphabet)

Deals with:
relation between sounds and phonemes (units which might have some function on the upper level)
e.g.: [u] ~ oo (as in book), [æ] ~ a (cat); i ~ y (flies)
Phonology
(Surface « Lexical) Correspondence
“symbol-based” (no complex structures)
Ex.: (stem-final change)
lexical: b a b y + s (+ denotes start of ending)
surface: b a b i e s (phonetic-related: bébì0s)
German (umlaut) (satz ~ sentence)
lexical: s A t z + e (A denotes “umlautable” a)
surface: s ä t z e (phonetic: zæce, vs. zac)
Turkish (vowel harmony)
lexical: e v + l A r (~house)
surface: e v l e r
Morphology
Input:

sequence of phonemes (~ (lexical) letters)

Output:
sequence of pairs (lemma, (morphological) tag)

Deals with:
composition of phonemes into word forms and their underlying lemmas (lexical units) + morphological categories (inflection, derivation, compounding)
e.g. quotations ~ quote/V + -ation(der.V->N) + NNS.
Morphology: Morphemes & Order
Handles what is an isolated form in written text

Grouping of phonemes into morphemes
sequence deliverables ~ deliver, able and s (3 units)
could as well be some “ID” numbers:
e.g. deliver ~ 23987, s ~ 12, able ~ 3456

Morpheme Combination
certain combinations/sequencing possible, other not:
deliver+able+s, but not able+derive+s; noun+s, but not noun+ing
typically fixed (in any given language)
Morphology: From Morphemes to Lemmas & Categories
Lemma: lexical unit, “pointer” to lexicon
might as well be a number, but typically is represented as the “base form”, or “dictionary headword”
possibly indexed when ambiguous/polysemous:
state1 (verb), state2 (state-of-the-art), state3 (government)
from one or more morphemes (“root”, “stem”, “root+derivation”, ...)

Categories:
small number of possible values (< 100, often < 5-10)
(Surface) Syntax
Input:
sequence of pairs (lemma, (morphological) tag)

Output:
sentence structure (tree) with annotated nodes (all lemmas, (morphosyntactic) tags, functions), of various forms

Deals with:
the relation between lemmas & morphological categories and the sentence structure
uses syntactic categories such as Subject, Verb, Object,...
e.g.: I/PP1 see/VB a/DT dog/NN ~
((I/sg)SB ((see/pres)V (a/det dog/sg)OBJ)VP)S
Syntax: Representation
Tree structure (“tree” in the sense of graph theory)
one tree per sentence

Two main ideas for the shape of the tree:
phrase structure (~ derivation tree, cf. parsing later)
using bracketed grouping
brackets annotated by phrase type
heads (often) explicitly marked
dependency structure (lexical relations “local”, functions)
basic relation: head (governor) - dependent
links (edges) annotated by syntactic function (Sb, Obj, ...)
phrase structure: implicitly present
Syntax: Phrase Structure Tree
Example:









((DaimlerChrysler’s shares)NP (rose (three eights)NUMP (to 22)PP-NUM )VP )S
Syntax: Dependency Tree
Example:










rosePred(sharesSb(DaimlerChrysler’sAtr),eightsAdv(threeAtr),toAuxP(22Adv))
Meaning (semantics)
Input:
sentence structure (tree) with annotated nodes (lemmas, (morphosyntactic) tags, surface functions)

Output:
sentence structure (tree) with annotated nodes (semantic lemmas, (morpho-syntactic) tags, deep functions)

Deals with:
relation between categories such as “Subject”, “Object” and (deep) categories such as “Agent”, “Effect”; adds other categories
e.g. ((I)SB ((see)V (Tom)OBJ)VP)S ~
(I/Sg/Pat (see/Perf/Pred) Tom/Sg/Ag)
...and Beyond
Input:
sentence structure (tree): annotated nodes (autosemantic lemmas, (morphosyntactic) tags, deep functions)

Output:
logical form, which can be evaluated (true/false)

Deals with:
assignment of objects from the real world to the nodes of the sentence structure
e.g.: (I/Sg/Pat (see/Perf/Pred) Tom/Sg/Ag) ~
see(Mark-Twain[SSN:...],Tom-Sawyer[SSN:...])[Time:bef 99/9/27/14:15][Place:39ş19’40”N76ş37’10”W]


Levels of formal description
Linguistic categories
Words, phrases, sentences
The Categories: Part of Speech:
Open and Closed Categories
Part of Speech - POS (pretty much stable set across languages)
morphological “behavior” is typically consistent within a POS category

Open categories: (“open” to additions)
verb, noun, pronoun, adjective, numeral, adverb
subject to inflection (in general); subject to cross-category derivations
newly coined words always belong to open POS categories
potentially unlimited number of words

Closed categories:
preposition, conjunction, article, interjection, particle
not a base for derivation (possibly only by compounding)
finite and (very) small number of words
The Categories: Part of Speech,
Open Categories: Nouns
Nouns: typically refer to entities
Inflection:
number singular, plural
gender feminine, masculine, neuter
case nominative, genitive, accusative, dative, vocative

semantic classification:
human/animal/(non-living) things: driver/bird/stone
concrete/abstract: computer/thought
common/proper: table/Microsoft

syntactic classification: countable/uncountable: book, water

morphological classification:
pluralia/singularia tantum: data (is), police (are)
“adverbial” nouns: afternoon, home, east (no inflection)
The Categories: Part of Speech,
Open Categories: Verbs
Verbs:
Inflectional:
subject number singular, plural
subject person first (I read), second (you read), …
tense present tense, past tense …
aspect progressive, perfect
modality possibility, …
voice active, passive

syntactic/semantic: classification:
ordinary: (to) speak, (to) write
auxiliaries: be, have, will, would, do, go (going)
modals: can, could, may, should, must, want
phasal: begin, end, start

morphological classification
conjugation type: regular/irregular, (Ge.: weak/strong/irregular)
conjugation class: (e.g. Italian: -are, -ere, -ire …)
The Categories: Part of Speech,
Open Categories: Pronouns
Pronouns:
Inflectional: number, person, gender, case
much like nouns (syntactic usage also similar)
(pro)noun ~ “stands for” a noun

classification (mostly syntactic/semantic):
personal: I, you, she, she, it, we, you, they
demonstrative: this, that
possessive: my, your, her, his, its, our, their; mine, yours, ours,...
reflexive: myself, yourself, herself,..., oneself
interrogative: what, which, who, whom, whose, that
indefinite (“nominal”): somebody, something, one
The Categories: Part of Speech,
Open Categories: Adjectives
Adjectives: describe properties of nouns

Inflectional: degree of comparison (comparative/superlative),
number, gender, case

classification:
ordinary: new, interesting, [test (equipment)]
possessive: John’s, driver’s
proper: Appalachian (Mountains)
often derived from verbs/nouns: teaching (assistant), trendy, stylish

morphological classification
degrees of comparison (En.: big, bigger, biggest)
usually requires agreement with the noun
The Categories: Part of Speech,
Open Categories: Adverbs
Adverbs: modify a verb, and specify place, time, manner, degree
Inflectional: degree of comparison

derivation from adjectives is common:
new  newly, interesting  interestingly
non-derived adverbs:
ordinary: so, well, just, too, then, often, there
wh-adverbs (interrogative): why, when, where, how
degree adverbs/qualifiers: very, too

morphological classification (not much, really...)
degree of comparison: well, better, best
soon, sooner
The Categories: Part of Speech,
Open Categories: Numerals
Numerals: used to indicate numbers
inflectional: number, gender, case, negation

open (infinite?) category: compounding (Ge.: einundzwanzig, 21)

classification:
cardinals: one, five, hundred
NB: million etc. often considered noun
ordinals: first, second, thirtieth
quantifiers: all, many, some, none
multiplicative: times, twice
multilateral: single, triple, twofold

morphological classification: as nouns/adjectives; many irregulars
The Categories: Part of Speech, Closed Categories
Closed categories: preposition, conjunction, article, interjection, clitic, particle

Morphological behavior: indeclinable
preposition: of, without, by, to;
conjunction:
coordinating: and, but, or, however
subordinating: that, if, because, before, after, although, as
Article (determiner): a, an, the
interjection: wow, eh, hello;
clitic: ‘s; may be attached to whole phrases (at the end)
particle: yes, no, not; to (+verb);
many (otherwise) prepositions if part of phrasal verbs, e.g. (look) up
The Categories: Number and Gender
Grammatical Number: Singular, Plural
nouns, pronouns, verbs, adjectives, numerals
computer / computers; (he) goes / (they) go
In some languages (Arabic): Dual (nouns, pronouns, adjectives)

Grammatical Gender: Masculine, Feminine, Neuter
nouns, pronouns, verbs, adjectives, numerals
he/she/it;
nouns: (mostly) do not change gender for a single lexical unit
Also: animate/inanimate (gram., some genders), etc.
Mädchen (Ge.; girl, neuter); děti (Cz.; children, masc. inanim.)
The Categories: Case
Case
English: only personal pronouns/possessives, 2 forms
other languages: 4 (German), 6 (Russian), 7 (Czech,Slovak,...), 5 (Romanian)
nouns, pronouns, adjectives, numerals

most common cases (forms in singular/plural)
nominative I/we (work) eu/noi (Ro)
genitive (picture of) me/us a mea/al meu
dative (give to) me/us mie
accusative (see) me/us pe mine
vocative you! tu!
locative (about) me/us (Czech)
instrumental (by) me/us (Czech)
The Categories: Person, Tense
Person
verbs, personal pronouns
1st, 2nd, 3rd: (I) go, (you) go, (he) goes; (we) go, (you) go, (they) go
merg, mergi, merge mergem mergeti merg (Ro)
Tense (Ro) (Pol.: go)
past: (you) went ai mers szliście
present: (you pl.) go mergeti idziecie
future (!if not “analytical”) (you) will go veti merge -
concurrent (gerund) going mergind idąc
Note on Tense
Examples of (traditional) tense:
infinitive: (to) write (tenseless, personless, ..., except negation (Cz.))
simple present/past: (I) write/(she) writes; (I,she) wrote
progressive present/past: (I) am writing; (I) was writing
perfect present/past: (I) have written; (I) had written
all in passive voice, too:
(the book) is being/has been/had been written etc.
all in conditional mood, too (mood: in Eng. not a morph. category)
(the book) would have been written
The Categories: Voice & Aspect
Voice
active vs. passive
(I) drive / (I am being) driven
(Ich) setzte (mich) / (Ich bin) gesetzt (Ge.: to sit down)
Aspect
imperfective vs. perfective:
пoкупал / купил (Ru.: I used to buy, I was buying) / I (have) bought)
imperfective continuous vs. iterative (repeating)
spal / spával (Cz.: I was sleeping / I used to sleep (every ...))
The Categories:
Negation, Degree of Comparison
Negation:
even in English: impossible (~ not possible)
Cz: every verb, adjective, adverb, some nouns; prefix ne-
It: some adjectives: irregular negation (s-, non )
Degree of Comparison (non-analytical):
adjectives, adverbs:
positive (big), comparative (bigger), superlative (biggest)
Pol.: (new) nowy, nowszy, najnowszy
Combination (by prefixing):
order? both possible: (neg.: Cz./Pol.: ne-/nie-, sup.: nej-/naj-)
Cz.: nejnemožnější (the most impossible)
Pol.: nienajwierniejszy (the most unfaithful)
Typology of Languages
By morphological features
Analytical: using (function) words to express categories
English, also French, Italian, ..., Japanese, Chinese
I would have been going ~ (Pol.) szłabym
Inflective: using prefix/suffix/infix, combines several categories
Slavic: Czech, Russian, Polish,... (not Bulgarian); also French, German; Arabic
Latin/Slavic: Romanian
(Cz. new(acc.)) novou (Adj, Fem., Sg., Acc., Non-neg., Pos.)
Agglutinative: one category per (non-lexical) morpheme
Finnish, Turkish, Hungarian
(Fin. plural): -i-
Categories & Tags
Tagset:
list of all possible combinations of category values for a given language

typically string of letters & digits:
compact system: short idiosyncratic abbreviations:
NNS (gen. noun, plural)
positional system: each position i corresponds to Ci:
AAMP3----2A---- (gen. Adj., Masc., Pl., 3rd case (dative), comparative (2nd degree of comparison), Affirmative (no negation))
tense, person, variant, etc.: N/A (marked by “empty position”, or ‘-’)
Famous tagsets: Brown, Penn, Multext[-East], ...
The Dictionary (or Lexicon)
Repository of information about words:
Morphological:
description of morphological “behavior”: inflection patterns/classes
Syntactic:
Part of Speech
relations to other words:
subcategorization (or “surface valency frames”)
Semantic:
semantic features
frames
...and any other! (e.g., translation)


Levels of formal description
Linguistic categories
Words, phrases, clauses, sentences
Words, Phrases, Clauses, Sentences
Words
smallest units on the syntax level
function/semantic

Phrases
consist of words and/or phrases; “constituents”

Clauses
have predicative meaning (single predicate)

Sentences
consist of clauses (one or more)
Words
Words
lexical units
auxiliary (function) words: have grammatical function
have meaning
idioms
fixed phrases (non-compositional) “hot dog”, “kick the bucket”

Relate to other words
dictionary: repository of information for each words about its (idiosyncratic) relations to other words
Phrases
Phrases
sequences of words and/or phrases (i.e. of constituents)
may be discontinuous, sometimes

Types of Phrases:

Simple/Clausal (i.e. clauses, which consist of phrases, behave like phrases... recursively!)

According to head type:
Noun phrase: a new book
Adjective phrase: brand new
Adverbial phrase: so much
Prepositional phrase: in a class
Verb phrase: catch a ball
Noun Phrases
Head: noun
water
a book
new ideas
that small village
The greatest rise of interest rates since W.W.II within a single year
an operating system which, despite great efforts on the part of our administrators, fails all too often
Adjective Phrases
Head: adjective
Simple APs very common, complex APs rare
old
very old
really very old
five times older than the oldest elephant in our ZOO
(was) sure, as far as I know, to be there first
Adverbial and Numerical Phrases
Head: adverb
three times as much
quickly
really
(... speaks) more loudly than anybody could imagine
yesterday
Numerical Phrases
(... lasted) three hours
twenty-two
Prepositional Phrases
Head: preposition
In fact, play the role of Adverbial Phrases often
in the City
at five o’clock
to a brightest future
without a glitch
to the point where neither of them could get out of it
up to five points
instead of Charles
Verb Phrases
Head: verb
(It) rains
... could ever see a large Unidentified Flying Object
..., why (we) have got so much rain
Please!
On Sunday, (he) was driven to the hospital
(It) began to snow
(...) prohibits smoking in this area
Coordination of Phrases
“Head”: conjunction, punctuation
and, or, but
cats and dogs
new or even newer
quickly and precisely
he came to the conclusion that it makes no sense to hide himself anymore and therefore we could hear him today
(flights) from and to Dallas
eat your lunch now or at the picnic table
Clauses
Predicative function:
some activity of some subjects/objects, somewhere in time, under certain circumstances

Main clause
not part of a greater clause

Embedded clause
part of other clause, having some function (like a phrase)

A tile falling from the roof nearly killed him.
He fell asleep while listening to the news.

Function of a Clause
same as for phrase, plus some (direct speech etc.)
Sentences
Consist of a single or several main clauses
If several main clauses:
coordination, much like coordinated phrases
more coordinating conjunctions:
and, or, but, (and) therefore, ...
In written text, starts with a capital letter
Ends by period/question mark/exclamation mark
not all periods end a sentence! – example?
Sometimes even semicolon (;) might be a sentence break (...vague)