modal

A verb that combines with another verb to indicate mood or tense. A modal (also known as a modal auxiliary) expresses necessity, uncertainty, ability, or permission.

Most linguists agree that there are 10 core or central modals in English: can, could, may, might, must, ought, shall, should, will, and would. Other verbs--including need, had better and invariant be--may also function as modals (or semi-modals).

Unlike other auxiliaries, modals have no -s, -ing, -en, or infinitive forms. (Because ought requires a to-infinitive complement, some linguists regard it as a marginal modal.)

See also:

• Auxiliary
• Future-in-the-Past
• Habitual Past
• Idiom
• Lexical Modality
• Marginal Modal
• Modality
• NICE Properties
• Primary Verbs
• Putative Should
• Semi-Auxiliary
• Sequence of Tenses (SOT)
• Shall and Will
• Verb Phrase

Etymology:

Examples and Observations:

• "When I was younger I could remember anything, whether it happened or not."
  (Mark Twain)



• "[G]overnment of the people, by the people, for the people, shall not perish from the earth."
  (Abraham Lincoln, The Gettysburg Address, 1863)



• "There are many things that we would throw away if we were not afraid that others might pick them up."
  (Oscar Wilde)



• "A modal auxiliary has the following characteristics:
  
  
  • Takes negation directly (can't, mustn't).
  • Takes inversion without DO (can I? must I?).
  • 'Code' (John can swim and so can Bill).
  • Emphasis (Ann COULD solve the problem).
  • No -s form for third-person singular (*cans, *musts).
  • No non-finite forms (*to can, *musting)
  • No co-occurrence (*may will)
  The first four of these are what Huddleston (1976: 333) calls the NICE properties (Negation, Inversion, Code, Emphasis) and they very clearly draw a dividing line between auxiliaries and main verbs, a line which would be far from clear if we tried to use semantic characteristics. The last three, which are specifically 'modal' criteria (see Palmer 1979: 9), are needed to exclude the auxiliaries BE, HAVE, and DO."
  (Jennifer Coates, The Semantics of the Modal Auxiliaries. Routledge, 1983)



• "As early as Old English, a group of verbs signaling modal characteristics of action share morphosyntactic and semantic features which later result in the formation of the category of modal auxiliaries. . . .
  
  "The most important syntactic developments which distinguish [modals] from other verbs are the following: (1) they lost their non-finite forms and their ability to take non-verbal objects; (2) the preterite forms came to be used in the present, future or timeless contexts; (3) they did not develop the to- link with an infinitive (in the Southern standard); (4) they became more and more uncommon in contexts where they were not followed by an infinitive."
  (Richard M. Hogg, et al., The Cambridge History of the English Language: 1476-1776. Cambridge Univ. Press, 1999)



• Modals and the Subjunctive
  "Modals are also used where some languages would use the subjunctive mood. The Modern English subjunctive is very restricted and examples are given in (11a) and (12a). Alternatives using modals are provided in (11b) and (12b):

  (11a) They insisted that he go. (subjunctive mood)
  (11b) They insisted that he should go.
  (12a) I wish it were Friday. (subjunctive mood)
  (12b) I wish it would be Friday.

  Since subjunctives are not common in Modern English, I will not go into this more deeply."
  (Elly Van Gelderen, An Introduction to the Grammar of English, rev. ed. John Benjamins, 2010)