Brief introduction to morphology

1
Brief introduction to morphology

• Morphology is the study of word structure and
  word formation processes in language.

2
Terminology

• A morpheme is the smallest meaning-bearing unit
  in a language.
• Free morphemes are independent words.
• Bound morphemes, called affixes, cannot stand on
  their own.
• Types of affixes
• prefix attaches at front of word
• suffix attaches at end of word
• circumfix attaches around word
• infix attaches inside word

3
References for examples

• Examples are either from our textbook or from
  Linguistics, second edition, by Akmajian, Demers
  and Harnish, MIT press.

4
Morphological processes

• There are different kinds of morphological
  processes, in particular
• inflectional morphology
• derivational morphology

5
English inflectional morphology

• nouns
• plural marker -s (dog s dogs)
• possessive marker -s (dog s dogs)
• verbs
• 3rd person present singular -s (walk s
  walks)
• past tense -ed (walk ed walked)
• progressive -ing (walk ing walking)
• past participle -en or -ed (eat en eaten)
• adjectives
• comparative -er (fast er faster)
• superlative -est (fast est fastest)

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Properties of (English) inflectional morphology

• Inflectional morphology does not change
  grammatical category
• In English, all inflectional affixes are suffices
  (they attach to the end of a word)
• Inflectional affixes are attached after any
  derivational affixes
• modern ize s modernizes (OK)
• modern s ize (NOT OK)
• modern ize s able (NOT OK)
• Inflectional morphology carries a regular meaning
  transformation.

7
English derivational morphology

• Derivational morphology can (but need not) change
  grammatical category.
• un do undo (both verbs)
• program able programmable (verb, adjective)
• Derivational morphology does not always induce a
  regular/predictable meaning change there is
  drift
• fix able fixable (able to be fixed)
• read able readable (more than just able to
  be read)
• wash able washable (more than just able to
  be washed)

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Concatenative vs. nonconcatenative morphology

• Concatenative morphology combines morphemes by
  concatentation (prefixes and suffixes demonstrate
  this)
• Non-concatentative morphology combines in a
  non-concatenative manner
• circumfixes and infixes
• templatic morphology

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Circumfix example

• German
• sagen (to say)
• ge-t (past particple circumfix)
• sagen ge-t ? gesagt (said)

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Infix example

• Bontoc Igorot (Philippine language)
• kayu (wood)
• -in- (product of a completed action)
• kayu -in- ? kinayu (gathered wood)
• English
• abso-bloody-lutely (emphasis)

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Templatic morphology

• Semitic languages (Arabic, Hebrew)
• stem (root), e.g. ktb (write)
• consonant-vowel (CV) template CVCCVC (causative)
• vocalization ui (perfect passive)
• Combination consonants in stem map onto Cs in
  template, vowels in vocalization map onto Vs to
  yield surface form kuttib (will have been
  written)

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Example detail
k t b
C V C C V C
? kuttib
u i
13
Parsing

• refers to the recovery of structure from analysis
  of input
• often refers to the processing of sentences
• can also refer to the processing of words
• Stemming refers to the recovery of a word stem
  given a surface form of the word
• uncharacteristically un character istic
  ally

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Lexicons

• One approach list all words
• difficult in English because some morphology is
  productive
• (table adapted from page 62 of text)

STEM walk merge try map
-s walks merges tries maps
-ing walking merging trying mapping
-ed walked merged tried mapped
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Issues

• Not only do some affixes attach to large numbers
  of stems,
• they also attach to new words in the language
• spam, spams, spamming, spammed, spammer
• Idea encode morphological rules to generate all
  forms of words from a minimal set of word stems.

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Applications

• lexicons
• stemming
• generating correct surface word forms

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Try it out!

• http//www.xrce.xerox.com/competencies/content-ana
  lysis/arabic/input/keyboard_input.html
• We discovered in lecture that this particular
  demo is broken, but that the site has lots of
  other nifty demos.