Semantics Agenda Natural Language Understanding NLU Semantics Definition

Semantics

Agenda • Natural Language Understanding (NLU) • Semantics • Definition • Semantic Analysis • Semantic features • Semantic role (thematic role) • Relationship between words • Theories in Semantics • Reading Material Natural Language Processing (NLP) by Rahman Ali, Lect: QACC, UOP 2 18 February 2021

Semantics Definition • Semantics is a branch of linguistics dealing with the meaning of words, phrases and sentences. [Kamil Wiśniewski, Aug. 12 th, 2007, Semantics (http: //www. tlumaczenia-angielski. info/linguistics/lexical- semantics. htm)] Natural Language Processing (NLP) by Rahman Ali, Lect: QACC, UOP 3 18 February 2021

Semantics (Cont. . ) • It is concerned with the conceptual meaning and not the associative meaning. • Conceptual meaning • Tells us what a word in fact denotes, as for example Friday the 13 th is a day between Thursday the 12 th and Saturday the 14 th, and that is the conceptual meaning of the phrase Friday the 13 th. • Associative meaning • Yet, for many people the idea of the day “Friday 13 th” brings either thoughts of bad luck or misfortune or happiness. • Pragmatics deals with associative meaning. Natural Language Processing (NLP) by Rahman Ali, Lect: QACC, UOP 4 18 February 2021

Semantic Analysis • Meaning of a word, phrase or sentence can be analyzed from its different aspects: • Semantic features • Semantic role (thematic role) • Relationship between words Natural Language Processing (NLP) by Rahman Ali, Lect: QACC, UOP 5 18 February 2021

Semantic Features Ø Basic elements which enable the differentiation of meaning of words. Natural Language Processing (NLP) by Rahman Ali, Lect: QACC, UOP 6 18 February 2021

Semantic Role (thematic role) • Describe the way in which words are used in sentences and the functions they fulfill. • Agent • The entity that performs an action is known as an agent, • Theme • While the entity involved in an action is called theme (or ‘patient). • Instrument • When an agent uses an entity in order to do something this entity is called an instrument. • Experiencer • When a person in a sentence does not perform any action, but only has a perception, state of feeling then the role is described as experiencer. • Location • The location is where an entity is, • Source • Is the initial position of the entity, the place where it moves from • Goal • The goal is where the entity moves to. Natural Language Processing (NLP) by Rahman Ali, Lect: QACC, UOP 7 18 February 2021

Semantic Role (Cont. . ) • • Agent (Anne Marshall), Theme (the ball), Instrument (her new golf club), Experiencer (she), Location (the hole), Source (the woods), Goal (the grassy area), • (2010 George Yule. The Study of Language (4 th edition), Cambridge University Press). Natural Language Processing (NLP) by Rahman Ali, Lect: QACC, UOP 8 18 February 2021

Relationship Between Words • Synonyms • Are two words with very similar, almost identical meaning, such as buy and purchase, or cab and taxi. • In some cases however, although the meaning seems nearly identical there is a difference in the word usage or the level of formality and therefore the words can not always be substituted. • Antonyms • In this type of relationship between words two words have opposite meanings, the words such as male/female, old/new, interesting/boring are antonyms. • Gradable antonyms • are opposites along a scale in that when someone says ‘I am not high’ it does not necessarily mean ‘I am short’. • Non-gradable antonyms • do not present such flexibility: when we say ‘I am married’ the only antonym available in this sentence would be ‘I am single’. Natural Language Processing (NLP) by Rahman Ali, Lect: QACC, UOP 9 18 February 2021

Relationship Between Words (Cont. . ) • Hyponymy • Sometimes the meaning of one word is included in the meaning of another, broader term. Then the relationship between words can be described as hyponymy as in the case of words: vegetable and carrot. A carrot is necessarily a vegetable, therefore the meaning of the word vegetable is included in the word carrot, so carrot is a hyponym of vegetable. • Superordinate • In this relation the word vegetable is the superordinate (higher level term) of the word carrot. • The relationship of hyponymy and superordination can be illustrated by the following diagram: Natural Language Processing (NLP) by Rahman Ali, Lect: QACC, UOP 10 18 February 2021

Relationship Between Words (Cont. . ) • Homophones • are words which have different written forms, but the same pronunciation such as: right/write, to/too/two, bear/bare. Homophones are often mistaken for homonyms, but • Homonyms • Words which have the same written or spoken forms and unrelated meanings, as for example: bat (flying creature) and bat (used in baseball), race (contest) and race (ethnic group). • Polysemy • When a word has multiple related meanings then linguists speak of polysemy as with head for instance: head as a part of body; mind, or mental ability; a person in charge. • Metonymy • There exist a close connection of certain entities in everyday experience. The connection can be that of container-content, whole-part, or others. It is clearly visible in the following example ‘he drank the whole bottle’ when it is obvious that he did not drink the container, but the content of the bottle. Natural Language Processing (NLP) by Rahman Ali, Lect: QACC, UOP 11 18 February 2021

Theories in Semantics • Model Theoretic Semantics • Truth-Conditional Semantics • Lexical & Conceptual Semantics • Lexical Semantics • Computational Semantics (http: //en. wikipedia. org/wiki/Semantics) Natural Language Processing (NLP) by Rahman Ali, Lect: QACC, UOP 12 18 February 2021

Reading/References • Yule G. 1996. The study of language. Cambridge: CUP. • (http: //en. wikipedia. org/wiki/Semantics) • Daniel Jurafsky, Speech and Language Processing: An Introduction to Natural Language Processing, Computational Linguistics and Speech Recognition • Kamil Wiśniewski, Aug. 12 th, 2007, Semantics (http: //www. tlumaczenia-angielski. info/linguistics/lexical-semantics. htm) Natural Language Processing (NLP) by Rahman Ali, Lect: QACC, UOP 13 18 February 2021