Appendix:English modal verbs

Appendix:English modal verbs

Introduction
This is a brief overview of modal auxiliary verbs in common usage in English.

It is intended to be orientative, showing how English modal verbs can vary in their modal functions. It is not intended to be an in-depth complete grammar on the subject. The examples are here to give a grammatical glimpse at the uses. However, it must be borne in mind that without context, the examples will be one-dimensional. The choice of modal verb at any time depends overwhelmingly on the nuances needed in any conversational exchange, or written piece.

Examples of English modal verbs: can, could, will, would, shall, should, may, might, must, ought, need and dare

Examples of English modal verbs – negative contractions: can’t, couldn’t, won’t, wouldn’t, shan’t, shouldn’t, mayn’t, mightn’t, mustn’t, oughtn’t, needn’t and daren’t

Some other constructions with modal functionality: be able to, have to, would rather, would like to, had better, bound to

Typical moods described: While, in linguistics, English modal verbs are said to have only three basic modalities (epistemic, deontic, dynamic), in common usage it is more practical to sub-divide these into some clearly recognisable modal functions.
 * ability, obligation, permission, requests, suggestions, promises, probability, possibility, necessity, advice, criticism, courage, preference – and some of their opposites –
 * inability, prohibition, freedom from obligation, lack of permission, improbability, impossibility, avoidability, lack of courage

Present

 * can: – I have the ability to play the piano.


 * can’t: – I do not have the ability to play the violin.


 * be able to: – I have the ability to play the piano.


 * be able to: – I do not have the ability to play the violin.


 * Usage Note: Stative verbs, (verbs which do not normally use a continuous inflection - See Category:English stative verbs), especially verbs of perception such as "see", "hear", "feel", etc. commonly use "can" to indicate the continuous sense. E.g. "I can see my house from here." Not "I am seeing my house from here". "I can feel a lump on my hip." Not "I am feeling a lump on my hip"  "I can understand some of what she is saying." Not "I am understanding some of what she is saying."

Future

 * Note: Can does not have a future inflexion, and will can is not grammatically possible.


 * will + be able to: – I will have the ability to play the piano.


 * will + not + be able to: – I will not have the ability to play the violin.

Past

 * could: – I had (used to have) the ability to play the piano.


 * couldn’t: – I did not have the ability to play the violin.


 * be able to: – I had the ability to play the piano.


 * be able to: – I did not have the ability to play the violin.


 * Note: The choice between could and be able to is often, but not always, based on using could for a general modality, and be able to for a particular occasion. E.g. – I couldn’t play the piano, but I was able to play Chopsticks if and when required.

Modals

 * Note: Can + any other modal verb is not grammatically possible. So “be able to” is employed instead.


 * Examples: I should be able to play the piano. – I might not be able to play the piano. – and so on.

Interrogative

 * can: – Do you have the ability to play the piano?


 * be able to: – Do you have the ability to play the piano?


 * could: – Did you have the ability to play the piano? – However – this use of “could” is ambiguous, and would usually be reserved for a simple polite request to play the piano.


 * be able to: – Did you have the ability to play the piano?

Present and Future
In present and future, there are degrees of obligation (a), Or prohibition (b): 1. The speaker believes that there is an obligation / prohibition. The speaker has authority to impose, or believes that the authority is correct.
 * (a) must:


 * (b) mustn’t:

2. The speaker believes that there is an obligation / prohibition. The speaker does NOT have authority to impose, or believes that the authority is overly strict.
 * (a) have to:


 * (b) can’t: – (Note that “don’t have to” does NOT mean prohibition.)

3. The speaker believes that there is probably an obligation / prohibition. The speaker is advising of the existence of this.
 * should:
 * ought:


 * shouldn’t:
 * oughtn’t:

Past

 * Note: “Must” has no past inflexion. The past inflexions of “have to” are used for obligation, and “couldn’t” is used for prohibition.
 * have to:


 * couldn’t:

Modals

 * Note: Modal verbs cannot be used together in most dialects of English. Thus, in standard English, “have to” may be used for obligation:
 * Example: might + have to: – It is possible that I will be obliged to work on Sunday.

Interrogative

 * Note: “Must” or “have to” depending on the type of obligation perceived.
 * must:  – Is there an obligation, imposed by authority, to get a license?
 * have to: – Am I obliged to go? – (I don’t really want to go, perhaps it is optional.).

Necessity

 * We have seen that must indicates absolute necessity to do. (Obligation). And mustn’t indicates absolute necessity NOT to do. (Prohibition).


 * While need is not a modal verb, however, needn’t is used modally to indicate absence of obligation, it is not necessary. Similarly, not have to also indicates absence of obligation.

Present

 * needn’t:
 * not have to:

Past
Note: compare normal verb need in past didn’t need to with modal verb needn’t have.
 * needn’t + have: – You got one, but it wasn’t necessary.
 * didn’t need to: – We didn’t get one, because it was not necessary.
 * didn’t have to: – Again, we didn’t get one, because it was not necessary.

Permission

 * There are many ways of asking for, and giving permission. The choice of modal verb often depends on contextual and subtextual influences such as degree of formality, etiquette, and expectations.

Requests for permission
Most formal to least formal:- -
 * Note: Permission requests are only made in first or third person. I, We, S/He, They.
 * might: – Formal, expecting a negative answer.
 * may: – Formal, expecting a positive answer.
 * could: – Peer request, no expectations.
 * can: – Informal, expecting a positive answer.
 * Also many variations of the form:, , and so on.

Giving permission
Most formal to least formal:-
 * Note: Granting permission is only made in second or third person. You, S/He, They.
 * may: – Formal
 * may: – Formal
 * can: – Informal
 * can’t: – Informal

Past

 * might: – Formal
 * could: – Informal

Requests
Simple requests. Most formal to least formal:-
 * There are many ways to request someone to do something. The choice of modal verb often depends on contextual and subtextual influences such as degree of formality, etiquette, and expectations.
 * Note: Requests for someone to do something are normally in second person only: You.
 * could: – Formal request
 * would: – Less formal request
 * can: – Informal request
 * will: – Very informal. More of an order than a request.
 * would you mind not: – Polite order to stop doing something.

Requests for help

 * Note: These help questions, when not posed directly with the verb, are often formed by “wh-” words + shall in first person. Also common are can and could.
 * shall:
 * can:
 * could:
 * could:
 * could:

Suggestions
shall:
 * Are a type of request, using shall or may in the first person.

may:

Present and Future
It is worth noting the firm promise expressed by will + continuous inflexion.
 * Promises are normally indicated by will and won’t.  "Shall" is sometimes used in formal contexts, such as business promises.
 * will:
 * won’t:
 * shall:
 * shall:
 * – Typically, pilots use this format as it implies an absolutely firm promise.

Past

 * would: – Reporting an earlier promise.
 * wouldn’t: – Reporting an earlier promise.

Refusal

 * Refusal can be personal, or ergative.
 * won’t: – Personal refusal to do something.
 * shan’t: – Personal refusal to do something. This form is not common, and is considered by some to be un-educated.
 * won’t:  – Ergative (“won’t” = “refuses to”), an object does not perform according to one’s wishes.

Probability and Improbability

 * Modal verbs are commonly used to express degrees of probability and possibility.

Future

 * Predictions, from certain to uncertain to certainly not.
 * will + “be -ing”: – I predict rain for tomorrow (I am certain. I have proof.).
 * will: – I predict rain for tomorrow (I could be wrong, but I think I am right.).
 * could: – I predict rain for tomorrow, possibly. (I think there is a good chance of rain.)
 * should: – Somebody said there would be rain, so perhaps there could be rain. (I don’t really know.).
 * might: – I predict there is about a 50% chance of rain.
 * mightn’t: – I predict there is about a 50% chance of no rain.
 * shouldn’t: – Somebody said there would not be rain, so perhaps it won’t rain. (I don’t really know.).
 * won’t: – I predict no rain for tomorrow (I could be wrong, but I think I am right.).
 * won’t + “be -ing”: – A dry day for tomorrow. (I am certain. I have proof.).

Conditional

 * In conditional expressions, modal verbs of probability and possibility are used in the result clause.
 * will: – Almost certain.
 * might: – A possibility.
 * won’t: – Almost certainly not.

Possibility and Impossibility
However, there are some expressions where modal verbs are used simply to express possibility:
 * While probability and possibility are two distinct concepts, they are intimately connected when expressed by modal verbs. If anything is expressed as probable, then, by logical inference, it is also possible. So, any of the expressions of probability can be used as an expression of possibility.

Future and Present

 * can: – Present possibility.
 * can: – Present and future possibility.
 * could: – This is a possibility.
 * may: – This is a possibility.
 * might: – This is a weak possibility.
 * must: – This is a logical certainty.
 * can’t: – This is an impossibility.
 * couldn’t: – This is a less likely possibility. It is probable.
 * bound to: – This is a logical certainty.
 * would: – This is a possibility.

Past

 * Note: modal + have + participle to indicate the past.
 * must + have: – This is a logical certainty. I have circumstantial evidence.
 * could + have: – It is possible that he did this. He had the opportunity.
 * may + have: – It is possible that he did this.
 * might + have: – It is possible that he did this. He had the motive. But
 * couldn’t + have: – It is unlikely that he did this, but not impossible.
 * can’t + have: – This is certainly impossible. I have proof.
 * could + have: – It didn’t happen, but it was possible.

Conditional

 * In conditional expressions, modal verbs of probability and possibility are used in the result clause.
 * can: – It is a real possibility.
 * could: – It is a possibility.
 * could: – It is a hypothetical possibility.
 * could + have: – It is a hypothetical possibility, in the past, which never happened.

Advice and Criticism and Regrets
Some advice can be construed as criticism:
 * Note: should and ought are associated with these two modes. They are interchangeable, but some consider ought to be a bit stronger than should. Also must and have to – normally associated with obligation – can be used for strong advice
 * should: – Advice to do.
 * shouldn’t: – Advice to stop doing.
 * ought: – Advice to do.
 * oughtn’t: – Advice to stop doing.
 * must: – Strong advice to do.
 * mustn’t: – Strong advice to stop doing.
 * have to: – Strong advice to do.
 * had better: – Strong advice to do.
 * shouldn’t:
 * ought + not:

Past

 * Note: should or ought + have. This structure is almost always criticism of a past action.
 * should + have:
 * shouldn’t + have:
 * ought + have:
 * ought + not + have:
 * Note: In first person, this structure is often used to express regret
 * should + have:

Preference

 * Note: would like to and would rather

Questions

 * would like to:
 * would rather:

Statements

 * would like to:
 * would rather:

Courage

 * Note: dare is associated with courage. Dare is used both as a modal verb and as a normal verb. The modal form is most commonly found in negative and interrogative phrases in the present.
 * Normal verb:
 * Normal verb:
 * Modal verb:
 * Normal verb:
 * Modal verb:
 * Modal verb:
 * Normal verb imperative order:

Tag Questions

 * Using modal verbs in tag questions is covered in Appendix:English tag questions.
 * Eg.

Would – past habit

 * would is sometimes used to denote habitual repeated actions in the past. Similar to used to, but not used with stative verbs.
 * would: – We used to go to the beach (as a repeated habitual action). It implies that we no longer do this.
 * used to: – “Would” cannot be used in this stative case.