• Morphology & its types.
• Approaches to Morphology
• Morpheme based morphology
• Morphological Analysis and its need.
• Morphological Generation and Analysis using
• Problems in Morphological Analysis.
• The study of word formation – how words are
built up from smaller pieces.
• Identification, analysis, and description of the
structure of a given language's MORPHEMES
and other linguistic units, such as root
words, affixes, parts of
speech, intonations and stresses, or
• Washing= wash + ing
• Browser= browse + er
• Rats= rat + s
Types of Morphology
• Inflectional morphology:-modification of a
word to express different grammatical
categories. Examples- cats, men etc.
• Derivational Morphology:- creation of a new
word from existing word by changing
grammatical category. Examples- happiness,
APPROACHES TO MORPHOLOGY
There are three principal approaches to
• Morpheme based morphology
• Lexeme based morphology
• Word based morphology
• Word forms are analyzed as arrangements
• Morphemes- smallest linguistic unit with a
Lexeme based Morphology
• Lexeme-based morphology usually takes what
is called an "item-and-process" approach.
• Instead of analyzing a word form as a set of
morphemes arranged in sequence, a word
form is said to be the result of applying rules
that alter a word-form or stem in order to
produce a new one
Word based Morphology
• Word-based morphology is (usually) a word-
• Instead of stating rules to combine
morphemes into word forms, or to generate
word forms from stems, word-based
morphology states generalizations that hold
between the forms of inflectional paradigms
• Analyzing words into their linguistic
• Ambiguity: More than one alternatives
flies fly VERB + PROG
fly NOUN + PLU
Input Morphologically analyzed output
Cats Cat+ N+ PL
Cat Cat + N + SG
Cities City + N + PL
Geese Goose + N + PL
Goose Goose + N + SG OR Goose + V
Gooses Goose + V + 3SG
Merging Merge + V + PresPart
Caught Catch + V + PastPart
Caught Catch + V + Past
NEED FOR MORPHOLOGICAL ANALYSIS
• Wastage of memory in exhaustive lexicon.
• Failure to depict linguistic generalization-
necessary to understand an unknown word.
• Morphologically rich and productive
languages might be problematic.
• Most NLP systems use simple linguistic
theories for morphological analysis.
• Most NLP systems widely use this approach.
• Words are related to each other by analogical
• Words can be categorized based on the
pattern they fit into.
• Applicable both to existing words and to new
• Application of a pattern different from the
one that has been used - give rise to a new
• Examples:-older replacing elder .
Procedure and Algorithm
• A language expert provides different tables of
word forms covering the words in the entire
• The roots follow the pattern( or paradigm )
implicit in the table for generating their word
EACH ENTRY IN THE TABLE SHOWS THE NUMBER OF
CHARACTERS TO BE DELETED FROM
Number Direct Oblique
Singular LADKAA LADAKE
Plural LADAKE LADAKON
Number Direct Oblique
Singular (0,ø) (1,e)
Plural (1,e) (1,ON)
The table can be expressed in terms of an algorithm, which is as
ALGORITHM 1: Forming paradigm table
PURPOSE: To form paradigm table from word forms table for a
INPUT: Root r, Words forms table WFT (with labels for rows and
OUTPUT: Paradigm table PT
1. Create an empty table PT of the same dimensionality, size and
labels as the word forms table WFT
2. For every entry w in WTF, do
then store “(0, Ø)” in the corresponding
position in PT
let i be the position of the first
characters in w and r which are
store (size(r)-i+1,suffix(i,w)) at the
corresponding position in PT
3. Return PT
Generation of a Word Form
ALGORITHM 2: Generating a word form
PURPOSE: To generate a word form given a root and
desired feature values.
INPUT: Root r, Feature values FV
USES: Paradigm tables, Dictionary of roots DR,
dictionary of indeclinable words DI
OUTPUT: Word w
1. If root r belongs to DI then return( words
stored in DI for r irrespective of FV)
2. let p = paradigm type of r as obtained from
3. let PT = paradigm table for p.
4. let (n,s) = entry in PT for feature values
5. w := r minus n characters at the end
6. w := w plus suffix s
PROBLEMS IN MORPHOLOGICAL
• False Analysis
• Bound base morphemes
Words such as hospitable, sizeable.
• They don’t have the meaning “to be able”
• They can not take the suffix -ity to form a
• Analyzing them as the words containing suffix
-able leads to false analysis
• Property of a morphological process to give rise
to new formations on a systematic basis.
Exceptions to the above rule.
Bound Base Morphemes
• Occur only in a particular complex word.
• Do not have independent existence.
• Words such as feasible, malleable
• -able has the regular meaning “be able”
• -ity form is possible
• Base words don’t exit independently
• “Linguistics, An Introduction to Language and
Communication” by Adrian Akmajian, Richard A.
Demers, Ann K. Farmer and Robert M. Harnish (5th
• SPEECH and LANGUAGE PROCESSING, An Introduction
to Natural Language Processing,
Computational Linguistics, and Speech Recognition by
Daniel Jurafsky and James H. Martin (Second Edition)
• “Natural Language Processing- a Paninian perspective”
by Akshar Bharati, Vineet Chaitanya, Rajeev Sangal.