Definition of modality from The Oxford Dictionary of English Grammar:
The expression of the speaker's opinions about present likelihood or about obligation: (a) (narrowly) by means of a modal auxiliary verb; (b) (more widely) using any of the linguistic means available.
1) Meanings that are to do with an ability to control things (root modality)
I can speak English.
You must come here at once.
2) Meanings that are to do with the speaker’s judgement about whether what s/he says is true (epistemic modality)
You may be right.
That must be the worst book ever written.
You are probably right.
Surely, that is the worst book ever written.
Modal auxiliaries proper: can, could, may, might, must, ought to, shall, should, will, would
Marginal modal auxiliaries: need, dare, have to, used to
Other expressions of modality:
a) modal adverbs, e.g. maybe, probably, surely, certainly
b) modal auxiliary equivalents, i.e. paraphrases of modal meanings (e.g. be possible, be willing to, be necessary that …)
Formal features of modal auxiliaries
· Act as auxiliaries and are followed by a bare infinitive: He can swim (Not *He can to swim.)
· Do not need do-support in negative and interrogative sentences: Can he swim? He can’t swim. (Not *Does he can swim? *He doesn’t can swim.)
· No 3rd person inflection: He can swim (Not * He cans swim.)
· No non-finite forms: * to can/could, musting
· Cannot be preceded by other auxiliaries: * He had could do it.
· No proper past tense, as the “past tense” forms do not normally refer to past time.
Root meanings of modal auxiliaries
ability (can/could): Can you swim?
permission (can/could, may/might): Can/may I leave the table?
obligation (must, ought to, shall/should): No, you must/ought to/should stay.
volition (will/would): I will leave the table anyway. I would leave the table if I were you.
possibility (may/might): Air fares within Europe may be increased.
prediction (will/shall): I won’t/shan’t be able to come, I’m afraid.
habitual activity (will/would): At such times he would stand and listen to the wind.
This is an important discovery
This must be an important discovery.
This should be an important discovery.
This could be an important discovery.
This may be an important discovery.
This might be an important discovery.
This isn't an important discovery.
Root and epistemic modality contrasted
1. Sarah can be very good at this.
2. Sarah can’t be very good at this.
3. Frank must think of a good excuse.
4. Frank must be thinking of a good excuse.
5. They must leave at two o'clock.
6. They must have left at two o'clock.
7. We should arrive by midday. 1) ... in order to be there in time for lunch.
2) ... unless the car breaks down.
8. You may be wrong.
9. That letter will be for me.
10.That must be the best film ever made.
11.I shouldn’t think so. / I wouldn’t have thought so.
12.Would you do me a favour, please?
You are wrong.
That letter is for me.
That’s the best film ever made.
I don’t think so.
(Will you) do me a favour
13.May I come in? Might I come in?
14.Going on holiday in bad weather may/might be a trying experience.
15.Can/could you do me a favour?
16.I wouldn’t do that. (past / present / future time reference?)
17.I could speak the language then, and I think I still can.
18.It may rain. à He said it might rain.
19.That will be a nuisance. à He said that would be a nuisance.
Modal auxiliaries and aspect
· Since modal auxiliaries have no non-finite form, they cannot be preceded by grammatical auxiliaries signalling progressive or perfective aspect
· If a modal auxiliary is followed by a progressive/perfective verb phrase, the modal is usually interpreted as epistemic.
20. The students must read the grammar book.
21. The students must be reading the grammar book.
22. The students must have read the grammar book.
Marginal modal auxiliaries: need, dare, have (got) to, used to
These verbs can behave in two different ways, as regards their grammatical properties:
· like modal auxiliaries (i.e. No s-form, no do-periphrasis, followed by bare infinitives): He needn't/daren't tell her. Need/dare he tell her?
· like lexical verbs/catenatives (i.e. s-form in 3rd person present tense, possibility of non-finite forms, followed by to-infinitive, do-periphrasis in negative and interrogative sentences): He needs/dares to tell her. Did he need/dare to tell her? Do you have to sing that loud? She used to sing to us. (Did she use(d) to sing to you?)
20. I don't need this handout. (lexical, main verb)
21. I don't need to read this handout. (catenative)
22. I needn't read this handout. (auxiliary)
23. He needn’t have been there. (root – obligation)
24. It needn’t have been him. (epistemic – possibility)
25. The money has (got) to be in their bank account by next Monday. (root – obligation)
26. Money has (got) to be the reason. (epistemic – degree of certainty)
Examples: be able to (»can)
be willing to (»will)
be obliged to (»must)
have permission to (»may)
be possible that (»may/might)
Note: these are not auxiliaries, but convey the same type of meanings as modal auxiliaries.
Marginal modals and modal auxiliary equivalents can be used to express more than one modal meaning in the same clause:
27. They will have to hand in the essay very soon. (willingness + obligation)
28. They might need to come earlier. (possibility + necessity)
29. I wouldn't dare to go to there on my own. (likelihood + willingness)
30. A computer ought to be able to do this. (necessity + ability)
31. Exporters won't be willing to support goods on credit. (prediction + willingness)
Marginal modals and modal auxiliary equivalents can be used to mark tense (particularly past tense) unambiguously:
32. It was not possible for them to be here. (= They might/could not be here?)
33. I had to hand in my essay. (= I must hand in my essay?)
34. The company were unwilling to support goods on credit. (=The company wouldn’t support goods on credit?)
Comparison with Norwegian
Non-finite forms and combination of modals
35. Han har aldri villet hjelpe meg.
36. Jeg har alltid måttet klare meg selv.
He has never been willing to help me.
I have always had to cope on my own.
37. Man må kunne forlange såpass.
38. Søkere vil måtte fylle ut dette skjemaet.
One must be allowed to demand as much.
Applicants will have to fill in this form.
39. Jeg vil/må hjem. I want to / have to go home.
40. Skal du ut? Are you going out?
41. Petter kan mye engelsk. Peter knows a lot of English.
42. Vi kan grønnsaker! * We can vegetables!
43. Truth will out!
Potential false friends among the modal auxiliaries
skal/shall (Note: shall is rare as a future marker, and is not used epistemically.)
· in questions (offers) shall works as a correspondence of skal with first-person subjects.
44. Skal jeg hjelpe til med oppvasken? Shall I help with the dishes?
45. Skal vi begynne? Shall we start?
46. Skal du ta toget? Are you going to / Will you take the train?
· in declarative sentences shall is sometimes used with first person subjects with the same meaning as Norwegian skal. With other types of subjects, shall means strong obligation.
47. Han skal komme i morgen. He will come / He is coming tomorrow.
48. Jeg skal dra snart. I shall/will leave soon. (I’m leaving soon.)
49. Du skal ikke engste deg. You mustn’t worry.
50. Du skal ikke stjele. You shall not lie.
51. Det skal ha vært tre ranere. Apparently/Allegedly there were three robbers.
skulle/should (Note: should is not used epistemically, and not in conditional constructions)
52. Du skulle (=burde) ikke ha gjort det. You shouldn’t have done it.
53. Han skulle kjøpe melk. He was going to buy milk.
54. Han sa han skulle parkere bilen. He said he would park the car.
55. Jeg skulle bare åpne vinduet. I was just going to open the window.
56. Hun skulle senere bli kirurg. Later she was to become a surgeon.
57. Du skulle vel ikke være broren til Per? You wouldn’t be Per’s brother, by any chance?
More about shall and should here (in Swedish)
vil/ville vs. will/would (Note: stronger element of willingness in Norwegian. Would is often epistemic or part of a conditional construction.)
58. Jeg vil gjerne ha litt vin. I would/should like some wine (please).
59. Hun vil bli forfatter. She wants to be a writer.
60. De skal/vil komme i morgen. They will arrive tomorrow.
61. Han ville ikke jobbe der. He didn’t want to work there. (He wouldn’t work there.)
62. Det ville vært lettere. That would have been easier.
More about will and would here (in Swedish)
(Note that both should and would are common in hypothetical constructions and as markers of politeness, distance, tentativeness, cf. 56, 57, and 61.)
Other expressions of modal meanings:
Modal disjuncts: She is probably / certainly in the library. (epistemic)
Constructions with anticipatory it. It is likely / possible that she is in the library. (epistemic)
It was obligatory for students to do physical exercises before classes. (root)
Tags: She’s in the library, isn’t she? … don’t you think? (epistemic)
“I think/believe …”: I think / believe / assume / trust she is in the library. (epistemic)