Word Classes and POS Tagging

English word classes

Types of classes

• closed class types - fixed membership

  e.g., preposition

• open class types - new words can be relatively easily added
  Major open classes (all occur in English; two occur in all known languages)
  • nouns
  • verbs
  • adjectives
  • adverbs

Determination of class

Open classes

Nouns - frequently person, place, or thing (i.e., noun is name given to the lexical class to which these often belong), but the lexical class is defined by the ability to

• occur with determiners
• take possessives
• occur in plural

Groupings

• proper nouns
• common nouns

• count nouns
• mass nouns

Verbs - frequently refer to actions and processes.

Chiefly distinguished by morphological forms

• tense
• number

Adjectives - modifier of a noun.

• qualities - red bike
• quantity; extent - two mules, vast ocean
• distinguishing - right hand page

• quality
• place
• time
• degree
• number

Closed classes

• prepositions - on, into, over
• determiners - a, an, the, those
• pronouns - he, she, I

  wh-pronouns: question form, complementizer

• conjunctions - and, but (usually means logical and)

• auxiliary verbs: e.g., can, may, should, are

  Properties -

  • negate sentence with word ``not'':
    I may go. cf. I may not go.
  • form questions by switching positions with subject:
    I may go. cf. May I go?
  • can occur without a full verb Yes, you may [go].
  • emphasize positive by acquiring the accent You will go.

  Express -

  • person - I am going. cf. You are going.
  • number I am going. cf. We are going.
  • mood - war was waged; war would be waged
  • tense - war was waged
  • primary - be, have, do
  • modal - can, could, may, might, shall, should, will, would, must;
      do not have distinctive third-person form in present tense
    marginal modal akasemi-modals - dare, need, ought to, used to;

• particles - article, preposition, conjunction, interjection, adverb
    expressing

  aspect of meaning - beat up (perfective aspect)
  connective relation - heart to heart; matter of little consequence
  limiting relation - book of learning; all but Joe (related to exclusive or)

• numerals