Parts of Speech

Grammars and Lexicons

11-721

Fall Term, 2003

Categories of Words:Parts of Speech

• Noun

• Verb

• Adjective

• Adverb

• Preposition

• Determiner (Article)

• Modal ?

Parts of Speech

This boy must seem incredibly stupid to that girl.Det Noun Modal Verb Adverb Adjective Prep. Det Noun

A note on scientific method

• Theories must be falsifiable.

• Results must be reproducible.

Reproducible Results: Chomsky, 1957

• The search for rigorous formulation in linguistics has a much more serious motivation than mere concern for logical niceties or the desire to purify well-established methods of linguistic analysis. Precisely constructed models for linguistic structure can play an important role, both negative and positive, in the process of discovery itself. By pushing a precise but inadequate formulation to an unacceptable conclusion, we can often expose the exact source of the inadequacy and, consequently, gain a deeper understanding of the linguistic data. More positively a formalized theory may automatically provide solutions for many problems other than those for which it was explicitly designed. Obscure and intuition-bound notions can neither lead to absurd conclusions nor provide new and correct ones, and hence they fail to be useful in two important respects.

Notional Definitions of Parts of Speech:(an example of “obscure and intuition-bound notions”)

• Verbs denote actions

• Nouns denote entities

• Adjectives denote states

• Adverbs denote manner

• Prepositions denote location

• Determiners specify

A Non-falsifiable Theory• Theory: noun denote entities• Counter-example: assassination is a noun that

denotes an event• Reply: no, it denotes the idea of the event, which

is an entity• How do you tell the difference between an event

and the idea of an event?• Without precise definitions, this theory cannot be

disproved.• (In language technologies, imprecise definitions

lead to poor intercoder reliability, which leads to poor training, etc.)

A Falsifiable Theory

• Only prepositions can be modified by right meaning completely or directly.

• Supporting Examples:– Right up/down/in/on/across the street– Right in the drawer– Right down the stairs– Right from school– Right across the street– *He right despaired.– *She chose right this one.

• Counter-examples: – She looked at him right strangely.

• (Right modifies an adverb.)– You look a right clown. (Oxford English Dictionary)

• (Right modifies a noun.)– The government made a right mess of it. (Oxford English Dictionary)

• (Right modifies another noun.)• The theory is falsified (if you like the counter-examples). It needs to be

refined (maybe by specifying which dialects it is valid for).

How do you decide the part of speech of a word?

• Distribution

• Morphology: Prefixes, suffixes, and other changes to the structure of the word.

Distribution of Parts of Speech

• Great ideas spread quickly.

• Interesting ideas spread quickly.

• Stupid ideas spread quickly.

• Colorless ideas spread quickly.

• Words of the same category have the same distribution. For example, adjectives can come before nouns.

Discussion:Distribution of parts of speech

• Great ideas spread quickly.• The ideas spread quickly.• Great idea spread quickly.

• Do great and the have the same part of speech?

• Do idea and ideas have the same part of speech?

Templates for testing parts of speech that work most of the time

• noun can be a pain in the neck.• Television can be a pain in the neck.• Linguistics can be a pain in the neck.• This can be a pain in the neck.• *Happy can be a pain in the neck.• *From can be a pain in the neck.• *The can be a pain in the neck.• *Breathe can be a pain in the neck.

What is wrong with this sentence?

• Cat can be a pain in the neck.

Templates for testing parts of speech that work most of the time

• They/it can verb.

• They/it can stay/leave/die/cry.

• *They/it can gorgeous/cute/trendy.

• *They/it can from/to/in/off/on.

• *They/it can door/bible/gold/camera.

What is wrong here?

• They can handle.

• They can accommodate.

• They can harbor.

Templates for testing parts of speech that work most of the time

• Modal I be frank?

• Can I be frank?

• Must I be frank?

• Should I be frank?

• Need I be frank?

Templates for testing parts of speech that work most of the time

• Very adverb or adjective

• Very slow

• Very slowly

• Very badly

• Very happy

Templates for testing parts of speech that work most of the time

• He treats her adverb.

• He treats her well.

• He treats her arrogantly.

• He treats her nicely.

• He treats her nice.

• He treats her good.

Templates for testing parts of speech that work most of the time

• They are very adjective.• They are very nice/gentlemanly/ladylike.• *They are very gentlemen/ladies/faxes.• *They are very starve/die.• *They are very to/at/on.

• They are very in.• They are very off.

Templates for testing parts of speech that work most of the time

• Right preposition.– Right is an intensifier.

• Right up/down/in/on/across the street• Right down the stairs• Right in the drawer• Right from school• Right across the street• *He right despaired.• *She chose right this one.

What about these sentences?

• She looked at him right strangely. (dialect)

• She is right pretty. (dialect)

• You look a right clown. (Oxford English Dictionary)

• The government made a right mess of it. (Oxford English Dictionary)

Templates for testing parts of speech that work most of the time

• He wrote determiner other works.

• He wrote the/all/these/no/few/many other works.

• *He wrote despair/be/have other works.

• *He wrote student other works.

• ?He wrote successful other works.

Words can have more than one part of speech

• He needs to see a doctor. (verb)

• Need there be a problem. (modal)

• I feel a need to explore my roots. (noun)

Morphology

• The form of words

• Affixes: Prefixes, suffixes, infixes

• Stem changes: swim/swam

• More about morphology in a couple of weeks.

Morphological properties of English nouns

• Count nouns– Cup/cups– Book/books

• Mass nouns– Attention/?attentions– Sand/?sands– Water/?waters– Coffee/?coffees

Morphological Properties of English adjectives

• Monosyllabic (one syllable) adjectives– Tall/taller/tallest– Fast/faster/fastest

• Multi-syllabic adjectives– Intelligent/more intelligent/most intelligent

Morphological Properties of English Verbs

Base Participle Past Present Gerund

mow mown mowed mows mowing

prove proven proved proves proving

go gone went goes going

meet met met meets meeting

cut cut cut cuts cutting

Invariant words: no prefixes or suffixes in English

• Prepositions (in, on, at, about, across, beyond, etc.)

• Modals (may, might, can, could, must, shall, should, etc.)

The Computational View

• Who cares if it is falsifiable? It just needs to be implementable.

• Non-falsifiable theories tend to be non-implementable.

Importance to you

• When you are building a lexicon, you will decide on parts of speech for words by using template tests and morphological tests.

Discussion• Toy house• Big house• Hypothesis 1: Toy is an adjective in toy

house. Toy house is just like big house.• Hypothesis 2: Toy is a noun in toy house.

Toy house is a compound noun.• Relevant diagnostic tests:

– Adjectives can be made comparative.– Adjectives can be modified by very.– Nouns can be made plural.

Discussion

• He is like his brother.

• Hypothesis 1: Like is an adjective.

• Hypothesis 2: Like is a preposition.

• Relevant diagnostic tests:– Comparatives– Very– Right

Part of Speech Tagging

• Input: string of words• Output: string of words with a part of speech

associated with each word.• Example:

– This:det boy:N likes:V that:det girl:N

• Use statistical or rule-based knowledge about distribution.

• Usually use a long list of parts of speech, e.g., around 40.