Linguistic Essentials

1. Linguistic Essentials

2. Parts of Speech and Morphology • Parts of Speech correspond to syntactic or grammatical categories such as noun, verb, adjectives and prepositions. • Word categories are systematically related by morphological processes such as the formation of plural form from the singular form.

3. Parts of Speech • Nouns, verbs, adjectives • Determiners • Adverbs She ran very quickly; She often travels to Vegas; She started off impressively. • Preposition She looked up the tree • Particles She looked up the number • Conjunctions, complementizer Funny but stupid She is afraid that ….

4. S --> NP VP NP --> DT NNS | DT NN | NP PP VP --> VP PP | VBD | VBD NP P --> IN NP DT --> the NNS --> children | students | mountains VBD --> slept | ate | saw IN --> in | of NN --> cake Syntax or Phrase Structure: A simple context-free grammar The Grammar The Lexicon

5. Syntax or Phrase Structure: A Parse Tree S NP VP AT NNS VBD NP The children ateAT NN the cake

6. Local and Non-Local Dependencies • Dependencies may be local e.g., DT NNS • A non-local dependency is an instance in which two words can be syntactically dependent even though they occur far apart in a sentence (e.g., subject-verb agreement; wh-extraction). • Non-local phenomena are a challenge for certain statistical NLP approaches (e.g., n-grams) that model local dependencies.

7. Semantic Roles • Most commonly, noun phrases are arguments of verbs. These arguments have semantic roles: the agent of an action, the patient and other roles such as the instrument or the goal.

8. Subcategorization • Different verbs can relate different numbers of entities: transitive versus intransitive verbs. • Verbs are classified according to the type of complements they permit. This called subcategorization. • FrameNet combines semantic roles and subcategorization. Let’s look up “put.v”

9. Attachment Ambiguity and Garden-Path Sentences • Attachment ambiguities occur with phrases that could have been generated by two different nodes in the parse tree. E.g.: The children ate the cake with a spoon. • Garden-Path sentences are sentences that lead you along a path that suddenly turns out not to work. E.g.: The horse raced past the barn fell.

10. Semantics • Semantics is the study of the meaning of words, constructions, and utterances. • Semantics can be divided into two parts: lexical semantics and combination semantics. • Lexical semantics: hypernymy, hyponymy, antonymy, meronymy, holonymy, synonymy, homonymy, polysemy (no need to memorize!). • Compositionality: the meaning of the whole is built up from the meanings of its parts different from its parts. (More on the next slide…)

11. Semantics:Idea of Strict Compositionality • The overall meaning of a phrase or sentence derives from the meanings of the constituent parts and the particular grammatical ways in which the parts are put together. • Let’s consider examples using the context free grammar we saw earlier …

12. S --> NP VP NP --> DT NNS | DT NN | NP PP VP --> VP PP | VBD | VBD NP P --> IN NP DT --> the NNS --> children | students | mountains VBD --> slept | ate | saw IN --> in | of NN --> cake Syntax or Phrase Structure: A simple context-free grammar The Grammar The Lexicon

13. While the constituent parts of a sentence and its grammatical structure are important for determining its meaning, strict compositionality often breaks down • Idioms are one area of language where meanings are not compositional; “to be at a crossroads” means “facing a decision or choice”

14. Pragmatics • Pragmatics is the area of studies that goes beyond the study of the meaning of a sentence and tries to explain what the speaker really is expressing. • Understand the scope of quantifiers, speech acts, discourse analysis, anaphoric relations.