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Modal verbs. Forms of Modals. Modals do not take third person -s √ The nurse can give the injection. x The nurse cans give the injection. The infinitive is used after the modal verb. √ The planes must take off now. √ The wastage can be stopped .
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Forms of Modals • Modals do not take third person -s √ The nurse can give the injection. x The nurse cans give the injection. • The infinitive is used after the modal verb. √ The planes musttakeoff now. √ The wastage canbestopped. √ The technical glitch could havebeen avoided. x She should recycles that paper.
Forms of Modals • In negative sentences, not follows the modal even when be or have are present. The investigation may not end today. √ The survey should not have yielded such results. √ The lecturer could not be there at this hour. √ The lecturer could be not there at this hour. x Do not use the contracted forms of negatives in formal writing. Use cannotand notcan’t .
Uses of Modals To express: • ability • degrees of possibility • advisability • necessity
Modals Expressing Degrees of Possibility cannot may/might not should must Unlikely highly likely • To express impossibility or near impossibility, use cannot. • To express low possibility, use may/may not; might/might not; or could/could not. • To express moderate possibility, use should/should not. • To express high possibility or probability, use must. • To express certainty or human intentions, use will/ will not. In the past context, use would/ would not. See Raimes (2006) pp. 74-75 for examples
Modals Expressing Degrees of Possibility She’s very intelligent and has been studying hard so she will pass the test. √ She’s very intelligent and has been studying hard. She should pass the test. √ She’s very intelligent and has been studying hard so she cannot pass the test. X
Modals Expressing Advisability • To express whether something is a good idea or not, use should or should not. • To express an advisable action that did not occur in the past, use should have + past participle. • To express a past action that was not advisable, use should not have+ past participle.
Modals Expressing Necessity • To express necessity, use must or has/have to. I must do my homework. (Must is internal) You have to wear a seatbelt when you drive. (Have to is external) • To express lack of necessity, use do/does/did + not + have to. I don’t have to do my homework. • To express a past necessity, use had to, not must . I had to do my homework last night. Must not expresses a prohibition, not a lack of necessity.
Common Error The opposite of must has two forms:
Sources Lane, A. and Lange, E. (1999). Writing Clearly: An Editing Guide (2nd ed.). Boston: Heinle and Heinle Publishers, 50-65 Raimes, A. (2006). Grammar Troublespots: A Guide for Student Writers (3rd ed.). New York: Cambridge University Press, 73-80.