Structure of a Lexicon Debasri Chakrabarti 13-May-19

Overview Categorial Component: a set of rules. Lexicon: containing a list of all the words in a language, together with a specification of their idiosyncratic syntactic, semantic, phonological and morphological properties. Lexicalization Principle: attaching lexical items under appropriate word-level category nodes. 13-May-19

Lexical Information Categorial Features Subcategorization Frames Selectional Restrictions Thematic Roles 13-May-19

Categorial Features For each item listed in the lexicon the grammar must specify which syntactic category it belongs to. Lexicon should say: boy is a noun dog can be either a noun or a verb need can function as a verb, a modal, or a noun Lexical entry for boy: [-V, +N] 13-May-19

Categorial Features There are four major word level categories – Verb, Adjective, Noun and Preposition. (Chomsky, Amherst Lectures, (1974)) These can be analyzed as complexes of two binary features: (nominal/ non-nominal) (verbal/ non-verbal) 13-May-19

Categorial Features These four major word-classes are broken down in the following way Verb = [+V, -N] Noun = [-V, +N] Preposition = [-V, -N] Adjective = [+V, +N] Capture supercategorial generalisation, i.e., generalisations which extend across more than one category 13-May-19

Categorial Features Lexical entry for boy: [-V, +N, +common, +Count] It is necessary to posit that a given category may belong to different categorial subclasses. Nouns Proper Nouns Common Nouns Count Nouns (can be used with a singular or plural determiner) Mass Nouns Lexical entry for boy: [-V, +N, +common, +Count] 13-May-19

Subcategorization Frame Traditional grammar: a given item is said to take a particular type of complement Recent terminologies: an item Subcategorizes a particular range of complements Why subcategorization frame is needed? 13-May-19

Subcategorization Frame VP NP I V` NP V John will Mary ? invite, kill, hit, harm, help come, go, wait, fall 13-May-19

Subcategorization Frame Subcategorization Frame does not depend on the meaning This is a kind of idiosyncratic information Example, I shall await your instruction. *I shall wait your instruction. It should be included in the lexicon 13-May-19

Intransitive Verbs Intransitive verbs : subcategorize zero complements Two different devices for expressing this a. come: Categorial Features : [+V, -N] Subcategorization Frame: [—Ø] b. come: Categorial Features : [+V, -N] Subcategorization Frame: [—] 13-May-19

Transitive Verbs Transitive verbs : subcategorize complements kill: Categorial Features : [+V, -N] Subcategorization Frame: [—NP] 13-May-19

Subcategorization Frame How to specify the Subcategorization Frame for a verb which can occur both in transitive and intransitive structure? John ate. John ate rice. eat: Categorial Features : [+V, -N] Subcategorization Frame: 13-May-19

Ditransitive verbs give: Categorial Features : [+V, -N] Subset of transitive verbs Takes two complements Example, John gave [Mary][ a book]. The postman handed [me] [a parcel]. give: Categorial Features : [+V, -N] Subcategorization Frame: [—NP NP] 13-May-19

Prepositional Complement Different Verbs take different PP complement headed by different Prepositions Example I defer [to/*at/*on/*by/*with your suggestion]. I put the book [on/*about/*with the table]. I can rely [on/*by/*to /*at/*with you]. rely: Categorial Features : [+V, -N] Subcategorization Frame: [—[PP(on) NP]] 13-May-19

Nouns and Adjectives Nouns and Adjectives can also take PP Complements obligatorily Example His reliance [on/*at/*to/*by/*with her help] *His reliance Mary is fond [of/*at/*to/*by/*with John]. *Mary is fond. reliance: Categorial Features : [-V, +N] Subcategorization Frame: [—[PP(on) ] fond: Categorial Features : [+V, +N] Subcategorization Frame: [—[PP(of)] 13-May-19

Prepositions Prepositions also permit a particular range of categories as their complement. Example I haven’t seen him [since the party]. I haven’t seen him [since the party began]. He left [during the party]. *He left [during the party was still going on]. since: Categorial Features : [-V, -N] Subcategorization Frame: during: Categorial Features: [-V, -N] Subcategorization Frame: [—NP] 13-May-19

Selectional Restrictions Semantic restrictions on the choice of expressions within a given category which can occupy a given sentence position. Differences between Subcategorization Frame and Selectional Restrictions are Subcategorization Frames are syntactic in nature Selectional Restrictions are purely semantic Verbs do not Subcategorize their Subjects Verbs impose Selectional Restrictions on their choice of Subject 13-May-19

Selectional Restrictions murder: Categorial Features: [+V, -N] Subcategorization Frame: [—NP] — murdered — John, knife, tree, lion Sam, knife, tree, lion Example, John murdered Sam. *John murdered the knife. *John murdered the lion. 13-May-19

Selectional Restrictions *John murdered the tree. *The knife murdered Sam. *The lion murdered Sam. murder requires both Human Subject and Object. murder: Categorial Features : [+V, -N] Subcategorization Frame: [—NP] Selectional Restrictions: <HUMAN — HUMAN> 13-May-19

Thematic Roles Each Argument (i.e., Subject or Complement) of a predicate bears a particular thematic role. (Gruber(1965), Fillmore(1968a) and Jackendoff (1972)) These are also known as theta-role or θ-role. The number of θ-roles associated with the Theory of Thematic Structure varies somewhat from author to author. There are some commonly assumed θ-roles. 13-May-19

Set of Theta Roles THEME (or Patient)= Entity undergoing some effect of an action, (Mary fall down) AGENT (or Actor)= Instigator of an action, (John killed Sam) EXPERIENCER = Entity experiencing some psychological state, (John was happy) BENEFACTIVE = Entity benefitting from some action (John gave a book to Mary) 13-May-19

Set of Theta Roles INSTRUMENT = Means by which something comes out (John killed Sam with a knife) LOCATIVE = Place in which something is situated or takes place (John put the book on the table) GOAL = Entity towards which something moves (John passed the book to Mary) SOURCE = Entity from which something moves (John took the book from the table) 13-May-19

Theta Roles John gave Mary a book. John bears the θ- role AGENT to the verbal predicate gave. Mary bears the role GOAL. Book bears the role THEME. A variety of linguistic phenomena can be accounted for in a more principled way Example, the verb roll can be used both in transitive and ergative structure Ergative structure is one in which the Object of a given transitive verb is used intransitively as the Subject of the verb 13-May-19

Ergative Verbs Example, In the first sentence the ball is the Object. John rolled the ball down the hill. The ball rolled down the hill. In the first sentence the ball is the Object. In the second sentence the ball is the Subject. The θ-role is same in both the cases, i.e., THEME. 13-May-19

Summarization Lexicon should comprise a set of lexical entries-specifying idiosyncratic properties Differentiate between subclasses of a category Distinguish between intransitive, transitive and ditransitive verbs Necessity of Selectional Restrictions Importance of Thematic Roles 13-May-19

Suggested Readings Andrew Radford, Transformational Grammar A First Course, Cambridge Textbooks in Linguistics, 1988. Noam Chomsky, Aspects of the Theory of Syntax, The MIT Press, 1964. 13-May-19