# Q1b · WordNet and its hierarchy

Subject: Natural Language Processing

Exam: TEE

Reader: https://deep-learning-study-room.vercel.app/nlp/#tee/papers/legacy-f23/q1b

Canonical: https://deep-learning-study-room.vercel.app/read/nlp/tee/papers/legacy-f23--q1b/

Previous examination · complete worked answers

**Question. Define WordNet. Describe the WordNet hierarchy.** [5 marks]

### Answer

**WordNet is a lexical database that groups word senses into synonym sets called synsets and links them through semantic and lexical relations.** It is a network of meanings, not merely a list of similar spellings.

A synset represents one concept. Its **lemmas** are the words that can express that concept. A **gloss** is a short definition, often accompanied by an example. An ambiguous word can occur in several synsets.

vehicle (general)

→

car / automobile (same concept)

→

sports car (specific)

This is a simplified teaching hierarchy, not a claim about every intermediate WordNet node. Going upward reaches hypernyms; going downward reaches hyponyms. Multiple parents can exist, so the structure need not be a single simple tree.

| Operation | Meaning | Illustration |
| --- | --- | --- |
| Get senses of a word | Find candidate synsets | bank → financial sense, river-edge sense, … |
| Get lemmas | Find synonyms within one synset | car, automobile, motorcar |
| Get definition/examples | Read the gloss and uses | Choose the intended concept |
| Get hypernyms | Move to broader categories | car → vehicle |
| Get hyponyms | Move to narrower categories | vehicle → particular vehicle categories |
| Get meronyms/holonyms | Find part/whole links | car ↔ wheel |

### WordNet versus a thesaurus

A thesaurus mainly groups related expressions for vocabulary lookup. WordNet explicitly distinguishes senses and labels relations such as hypernymy, hyponymy and meronymy. This supports WSD, query expansion, lexical similarity and semantic search.

### Three uses explained

1. **Search expansion:** a query for “automobile” can retrieve relevant documents using “car”. Expansion should use the right sense.
2. **WSD:** definitions of the senses of “bank” provide words that can be compared with the sentence context.
3. **Similarity:** concepts near one another in an “is-a” hierarchy tend to be semantically related. Path-based measures depend on which senses were selected.

WordNet mein spelling ka group nahi—meaning ka synset, aur meanings ke beech labelled links.