Morphology (CS 626-449)

Morphology (CS 626-449)By Mugdha BapatUnder the guidance of Prof. Pushpak Bhattacharyya

What is Morphology?washing-ingwashbatbatswritewriterratratsbrowsebrowser

Morphology for NLPMachine Translation

Information Retrievalgoose and geese are two words referring to the same root goose

AnalyzeGenerateTransfer: , Noun, Direct Case, Plural, Noun, Direct Case, Plural

Need of MA and MGWhy not list all the forms of a word along with their features?Drink: drink, V, 1st persondrink, V, 2nd persondrink, V, 3rd person, pluralDrinks: drink, V, 3rd person, singularDrank: Drunk: Drinking:

Need of MA and MGReasons:Productivity: going, drinking, running, playingStoring every form leads to inefficiencyAddition of new wordsVerb: To fax. Forms: fax, faxes, faxed, faxingMorphological complex languages: Marathi (SG)++(PL)+Meaning: PolymorphemicPossible to store all the forms?

MorphemesSmallest meaning bearing units constituting a word

StemPrefixSuffixAffixes in Hindi?

Classes of MorphologyInflectionDerivation

InflectionIndicates some grammatical function like

Results in a word of the same classProductivity

Case (D) (O) Number (Sg) (Pl)Person (1st) (2nd)Gender(Masc) (Fem)Tense(Pas) (Fem)

DerivationUsually, results in a word of a different class-able when attached to a verb gives an adjectiveread (V) + -able = readable (Adj)Often meaning of the derived word is difficult to predict exactlywriter :: writer (one who writes)paint :: painter (one who paints)cut :: cutter? (an instrument used to cut)Less productiveeatable :: readable :: runnable?

Problems in MAProductivity False AnalysisBound Base Morphemes

ProductivityProperty of a morphological process to give rise to new formations on a systematic basis

Exceptions

PeaceableActionableCompanionableSaleableMarriageableReasonableImpressionableFashionableknowledgeable

False analysis

Bound Base MorphemesOccur only in a particular complex word Do not have independent existence

More on InflectionInflectional Suffixes in English

Noun inflectional suffixesPlural marker -sPossessive marker sVerb inflectional suffixesThird person present singular marker -sPast tense marker -edProgressive marker -ingPast participle markers -en or edAdjective inflectional suffixesComparative marker -erSuperlative marker -est

Spelling RulesGenerally words are pluralized by adding s to the endWords ending in s, -z, -sh and sometimes x require es buses, quizzes, dishes, boxesNouns ending in y preceded by a consonant change the y to -i babies, floppies

Verbal InflectionForms governed by spelling rulesIdiosyncratic forms

Morphological Form ClassesRegularly Inflected VerbsIrregularly Inflected VerbsStemJumpParseFrySobEatBringCut-s formJumpsParsesFriesSobsEatsBringsCuts-ing participleJumpingParsingFryingSobbingEatingBringingCuttingPast formJumpedParsedFriedSobbedAteBroughtCuted participleJumpedParsedFriedSobbedEatenBroughtCut

Morphological ParsingFinding Constituent morphemesFeatures

InputMorphological Parsed Outputcatscat +N +PLgeesegoose +N +PLgoose(goose +N +SG) or (goose +V)goosesgoose +V +3Gcaught(catch +V +PAST-PART) or (catch +V +PAST)

Resources

LexiconList of stems and suffixes along with basic information about themMorphotacticsA model of morpheme ordering that explains which classes of morphemes can follow other classes of morphemesOrthographic RulesSpelling rules used to model the changes that occur in the work usually when two morphemes combine

Morphological RecognitionLexicon

reg-nounirregular-sg-nounirregular-pl-nounpluralflowergoosegeese-scatsheepsheepdogmousemice

Morphological Recognition: Nounsq0q1q2reg-nounplural (-s)irreg-pl-nounirreg-sg-nounNote: Here, we are ignoring the nouns which take the suffix es for pluralizationLexiconFSA

reg-nounirregular-sg-nounirregular-pl-nounpluralflowergoosegeese-scatsheepsheepdogmousemice

Adjectives

TypePropertiesExamplesadj-root1Occur with un- and -lyhappy, realAdj-root2Cant occur with un- and -lybig, red

Adjectivesq0q3q4q5q2q1un-adj-root1adj-root2adj-root1-er -ly -est-er -est

TypePropertiesExamplesadj-root1Occur with un- and -lyhappy, realAdj-root2Cant occur with un- and -lybig, red

ReferencesLinguistics, An Introduction to Language and Communication by Adrian Akmajian, Richard A. Demers, Ann K. Farmer and Robert M. Harnish (5th Edition)SPEECH and LANGUAGE PROCESSING, An Introduction to Natural Language Processing, Computational Linguistics, and Speech Recognition by Daniel Jurafsky and James H. Martin (Second Edition)

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