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Morphology (CS 626-449)

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Morphology (CS 626-449). By Mugdha Bapat Under the guidance of Prof. Pushpak Bhattacharyya. What is Morphology?. Study of Words Their internal structure How they are formed ? Morphology tries to formulate rules. washing. wash. - ing. bat. bats. rat. rats. write. writer. browse. - PowerPoint PPT Presentation

Text of 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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