Word Analysis
Morphological analysis is a foundational task in Natural Language Processing (NLP). It involves breaking down a word into its root and affix(es), which is essential for understanding word structure and meaning in any language.
1. What is Morphological Analysis?
Definition: Analysis of a word into root and affix(es) is called morphological analysis of a word. Identifying the root of a word is mandatory for any NLP task.
Example: Word Forms Across Languages
- English:
- Root: 'play'
- Forms: 'play', 'plays', 'played', 'playing'
- Hindi:
- Root: 'खेल' (khela)
- Forms: खेल, खेला, खेली, खेलूंगा, खेलूंगी, खेलेगा, खेलेगी, खेलते, खेलती, खेलने, खेलकर
- Telugu:
- Root: ఆడడం (Adadam)
- Forms: ఆడుతాను, ఆడుతున్నాను, ఆడేను, ఆడేం, ఆడేవా, ...
Checkpoint:
- Why is it important to identify the root of a word in NLP?
- Can you think of a word in your language that has many forms?
2. Morphological Richness
The number of forms a root word can take varies across languages. Indian languages are generally considered morphologically rich, meaning words can have many forms due to inflections and derivations.
Checkpoint:
- What challenges might arise in NLP for morphologically rich languages?
3. Types of Morphology
Inflectional Morphology
- Deals with word forms of a root where there is no change in lexical category.
- Example: 'played' is an inflection of 'play' (both are verbs).
Derivational Morphology
- Deals with word forms of a root where there is a change in lexical category.
- Example: 'happiness' is a derivation of 'happy' (adjective → noun).
Checkpoint:
- What is the difference between inflectional and derivational morphology?
- Give an example of each from any language you know.
4. Morphological Features
During morphological analysis, each word is assigned a lexical category and may take suffixes for features such as gender, number, person, case, tense, aspect, and modality.
Nouns & Pronouns
- Can take suffixes for: gender, number, person, case
Example Analyses
| Language | Input Word | Output Analysis |
|---|---|---|
| Hindi | लडके (ladake) | rt=लड़का(ladakaa), cat=n, gen=m, num=sg, case=obl |
| Hindi | लडके (ladake) | rt=लड़का(ladakaa), cat=n, gen=m, num=pl, case=dir |
| Hindi | लड़कों (ladakoM) | rt=लड़का(ladakaa), cat=n, gen=m, num=pl, case=obl |
| English | boy | rt=boy, cat=n, gen=m, num=sg |
| English | boys | rt=boy, cat=n, gen=m, num=pl |
Verbs
- Can take suffixes for: tense, aspect, modality, gender, number, person
Example Analyses
| Language | Input Word | Output Analysis |
|---|---|---|
| Hindi | हँसी(hansii) | rt=हँस(hans), cat=v, gen=fem, num=sg/pl, per=1/2/3 tense=past, aspect=pft |
| English | toys | rt=toy, cat=n, num=pl, per=3 |
Checkpoint:
- What features are typically analyzed for nouns? For verbs?
- Try analyzing a word from your language using these features.
5. Feature Glossary
- rt: root
- cat: lexical category (noun, verb, adjective, pronoun, adverb, preposition)
- gen: gender (masculine or feminine)
- num: number (singular (sg) or plural (pl))
- per: person (1, 2, or 3)
- tense: present, past, or future (for verbs)
- aspect: perfect (pft), continuous (cont), or habitual (hab) (for verbs)
- case: direct or oblique (for nouns)
Checkpoint:
- What is the difference between direct and oblique case in Hindi? Why doesn't English have this distinction?
Note:
- A case is oblique when a postposition occurs after a noun. If no postposition can occur after a noun, the case is direct.
- Some Hindi postpositions: का(kaa), की(kii), के(ke), को(ko), में(meM)
6. Summary
Morphological analysis is crucial for understanding and processing natural language, especially in morphologically rich languages like Hindi and Telugu. By breaking words into their roots and features, we can better analyze, translate, and generate language computationally.
Final Checkpoint:
- Why is morphological analysis especially important for Indian languages?
- How does it help in tasks like translation or information retrieval?