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v t e

Look up Appendix:English modal verbs in Wiktionary, the free dictionary.

The English modal auxiliary verbs are a subset of the English auxiliary verbs used mostly to express modality (properties such as possibility and obligation).^[a] They can most easily be distinguished from other verbs by their defectiveness (they do not have participles or plain forms^[b]) and by their lack of the ending ‑(e)s for the third-person singular.^[3]

The central English modal auxiliary verbs are can (with could), may (with might), shall (with should), will (with would), and must. A few other verbs are usually also classed as modals: ought, and (in certain uses) dare, and need. Use (/jus/, rhyming with "loose") is sometimes classed so as well. Other expressions, notably had better, share some of their characteristics.

Modal auxiliary verbs distinguished grammaticallyedit

A list of what tend to be regarded as modal auxiliary verbs in Modern English, along with their inflected forms, is shown in the following table.

Contractions are only shown if their orthography is distinctive. There are also unstressed versions that are typically, although not necessarily, written in the standard way.^[4] Where there is a blank, the modal auxiliary verb lacks this form. (A corresponding lexical verb may have the form. For example, although the lexical verb need has a preterite form, the modal auxiliary verb need does not.)

Criteria for modal auxiliary verbsedit

Descriptive grammars of English differ slightly on the criteria they set for modal auxiliary verbs. According to The Cambridge Grammar of the English Language, the criteria are as follows.

Auxiliary verbsedit

Modal auxiliary verbs are a subset of auxiliary verbs, and thus meet the criteria for these. For lists of these criteria, see the article English auxiliary verbs; but among them are that the verbs: (i) can invert with their subjects (notably in questions, Must I go?), (ii) can be negated with not (I must not go; Must I not go?),^[8] and (iii) have negative inflected forms (won't, wouldn't).^[9]

No untensed formsedit

To illustrate untensed forms, those of the irregular lexical verb take and the non-modal auxiliary verb be are the plain take and be (as in Take it!, I didn't take it, and Don't be silly), the gerund-participles taking and being, and the past participles taken and been.^[10]

Modal auxiliary verbs lack untensed forms. Attempting to use them brings ungrammatical results:

• *I will can drive if I take ten lessons.^[g]
• *Canning drive would be helpful.
• *I have could/canned drive since I was 18.

Compare the grammaticality of non-modal auxiliary verb be in I will be able to drive, being able to drive, and I have been able to drive.

No subject–verb agreementedit

This refers to agreement of a verb (in present tense) with its third-person singular subject:

• She can/*cans try.

Compare lexical verb try in She tries/*try, and non-modal auxiliary verb do in She does/*do try.

Had better and (as an auxiliary verb) used lack present tense forms. Other than in present tense, even lexical verbs lack subject agreement, so this test is inapplicable to either had better or used.

Only a bare infinitival clause as complementedit

Whereas the lexical verb seem takes a to-infinitival clause (It seemed to happen), and the non-modal auxiliary verb have takes a past participial clause complement (It has happened), a modal auxiliary verb can (in principle) only take a bare infinitival clause (a subordinate clause with the plain form of the verb, and without to) as its complement:

• It can be a surprise.
• *It can to be a surprise.
• *It can being a surprise.

If they are modal auxiliary verbs, then ought and used are exceptions to this (although ought is increasingly used with a bare infinitival clause complement).^[11]

Bare infinitival clause complements are not unique to modal auxiliary verbs. Do is a non-modal auxiliary verb that takes one (Did you move the piano?); help is a lexical verb that can do so (I helped move the piano).

Ability to occur in remote apodosisedit

An apodosis is the "then" half of a conditional statement. (The "if" half is the protasis.) Remote here means "thought by the speaker to be unlikely" or "known by the speaker to be untrue".

• If I were an elephant, I would eat more apples.

Compare lexical verb eat in *If I were an elephant, I ate more apples, and non-modal auxiliary verb be in *If I were an elephant, I was able to eat more apples.

Must satisfies this only for a minority of speakers, and it is questionable whether had better does so.^[12]

The Cambridge Grammar comments on may that:

here there is evidence that for some speakers may and might have diverged to the extent that they are no longer inflectional forms of a single lexeme, but belong to distinct lexemes, may and might, each of which – like must – lacks a preterite....^[5]

Used does not satisfy this.^[7]

Preterite usable in the main clause for modal remotenessedit

• I could drive there, I suppose.

If similarly intended (as a doubtful or incredulous contemplation of an option for the future), attempts at this with a lexical or non-modal auxiliary verb are ungrammatical: *I drove there, I suppose; *I was going to drive there, I suppose.

Other than when used for backshift, should has diverged in meaning so far from shall as to be usable here only with difficulty. As they lack preterite forms, must, ought and need cannot be used in this way, and so this criterion does not apply to them.^[13] And used describes the past, not the present or future.

Commentsedit

The following verbs, shown in present–preterite pairs, satisfy or come close to satisfying all of the above criteria, and can be classed as the central modal verbs of English:

• can (with could)
• will (with would)
• may (with might) – although the lack in today's Standard English of a negative present inflection (*mayn't) means that it fails one of the criteria for auxiliary verbs
• shall (with should) – although the semantic divergence of shall and should means that its success with one criterion is debatable
• must – although its lack of a preterite (see its etymology below) means that it neither passes nor fails one of the criteria

Even for lexical verbs, preterite forms have uses besides referring to the past; but for modal auxiliary verbs such uses are particularly important: (Could you pass me the sauce?; Without my phone I might easily be lost; You should work harder; I would avoid that street).

Ought, dare, need, and used satisfy some of the criteria above, and are more (ought, dare, need) or less (used) often categorized as modal verbs.^[14][15] Had better is sometimes called a modal idiom.

Other English auxiliary verbs appear in a variety of different forms and are not regarded as modal verbs. These are:

• be, used as an auxiliary verb in passive voice, continuous aspect and indeed in virtually all of its uses, even as a copula;
• have, used as an auxiliary verb in perfect aspect constructions and the idiom have got (to); it is also used in have to, which has modal meaning, but here (as when denoting possession (very broadly understood)) have only rarely follows auxiliary verb syntax;
• do, see do-support;
• to, of to-infinitival clauses (if to is a defective verb, and not a subordinator).^[16]

Lists of modal auxiliary verbsedit

Five recent scholarly descriptions of verbs disagree among themselves on the extension of modal auxiliary verb: on which verbs are modal auxiliary verbs.

They agree that can (with could), may (with might), must, shall (with should) and will (with would) are, or are among, the "central modal auxiliaries" (A Comprehensive Grammar of the English Language, 1985),^[17] "secondary or modal auxiliaries" (F. R. Palmer, 1988),^[18] "modal auxiliaries" (Anthony R. Warner, 1993),^[19] "central members of the modal auxiliary class" (The Cambridge Grammar of the English Language, 2002),^[20] or "core modal verbs" (Bas Aarts, 2011).^[21]

Among these five verbs, The Cambridge Grammar selects the pair can and will (with could and would) as "the most straightforward of the modal auxiliaries";^[22] Peter Collins agrees.^[23]

All five accord ought, need and dare a less clear or merely a marginal membership.^{[24][18][19][25][26]}

A Comprehensive Grammar and Warner do likewise for use;^[27][19] the other three deny that it is a modal auxiliary verb.^[28][7][29] For this reason it is primarily discussed not in this article but in the article English auxiliary verbs.)

As for would in would rather, would sooner and would as soon, and have in had better, had best and had rather, only The Cambridge Grammar notes all six, but each of the other four descriptions of auxiliary verbs notes three or more. Of the three to six idioms that each discussion does note, there is no variation in the status that it accords to them. Warner calls the three that he notes – would rather, had better, had rather – modal auxiliaries.^[19] Palmer says that the same three are not modal auxiliaries.^[30] Both A Comprehensive Grammar and Aarts use the term modal idiom for a choice of five.^[31][32] The Cambridge Grammar sees modal characteristics in all six uses of these two auxiliary verbs.^[33]

A Comprehensive Grammar calls both have got (I've got to go now) and be to (You are to hand over the cash) modal idioms.^[31] None of the other descriptions agrees.^{[34][35][36][37]}

Palmer calls be bound/able/going/willing to and have (got) to semi-modals.^[38] A Comprehensive Grammar calls be able/about/apt/​​bound/due/going/​​likely/meant/obliged/​​supposed/willing to and have to semi-auxiliaries, adding that "The boundaries of this category are not clear".^[39]

Etymologyedit

The modals can and could are from Old English can(n) and cuþ, which were respectively present and preterite forms of the verb cunnan ("be able"). The silent l in the spelling of could results from analogy with would and should.

Similarly, may and might are from Old English mæg and meahte, respectively present and preterite forms of magan ("may, to be able"); shall and should are from sceal and sceolde, respectively present and preterite forms of sculan ("owe, be obliged"); and will and would are from wille and wolde, respectively present and preterite forms of willan ("wish, want").

The aforementioned Old English verbs cunnan, magan, sculan, and willan followed the preterite-present paradigm (or, in the case of willan, a similar but irregular paradigm), which explains the absence of the ending -s in the third person on the present forms can, may, shall, and will. (The original Old English forms given above were first and third person singular forms; their descendant forms became generalized to all persons and numbers.)

The verb must comes from Old English moste, part of the verb motan ("be able/obliged (to do something)"). This was another preterite-present verb, of which moste was in fact the preterite (the present form mot gave rise to mote, which was used as a modal verb in Early Modern English; but must has now lost its past connotations and has replaced mote). Similarly, ought was originally a past form—it derives from ahte, preterite of agan ("own"), another Old English preterite-present verb, whose present tense form ah has also given the modern (regular) verb owe (and ought was formerly used as a preterite form of owe).

The verb dare also originates from a preterite-present verb, durran ("dare"), specifically its present tense dear(r), although in its non-modal uses in Modern English it is conjugated regularly. However, need comes from the regular Old English verb neodian (meaning "be necessary")—the alternative third person form need (in place of needs), which has become the norm in modal uses, became common in the 16th century.^[40]

Preterite formsedit

The preterite forms given above (could, might, should, and would, corresponding to can, may, shall, and will, respectively) do not always simply modify the meaning of the modal to give it past reference. The only one regularly used as an ordinary past tense is could, when referring to ability: I could swim may serve as a past form of I can swim.

All the preterites are used as past equivalents for the corresponding present modals in indirect speech and similar clauses requiring the rules of sequence of tenses to be applied. For example, if it were said in 1960 that People think that we will all be driving hovercars by the year 2000, it might now be reported that In 1960, people thought we would all be driving hovercars by the year 2000.

This "future-in-the-past" (also known as the past prospective) use of would can also occur in a main clause: I moved to Green Gables in 1930; I would live there for the next ten years.

In many cases, in order to give modals past reference, they are used together with the auxiliary have and a past participle, as in I should have asked her; You may have seen me. Sometimes these expressions are limited in meaning; for example, must have can refer only to certainty, whereas past obligation is expressed by an alternative phrase such as had to (see § Replacements for defective forms below).

Conditional sentencesedit

The preterite forms of modals are used in the apodosis (then-clause) of counterfactual conditional sentences. The modal would (or should as a first-person alternative) is used to produce the conditional construction typically used in clauses of this type: If you loved me, you would support me. It can be replaced by could (meaning "would be able (to do something)") and might (meaning "would possibly") as appropriate.

When the clause has past reference, the construction with the modal plus have (see above) is used: If they (had) wanted to do it, they would (could/might) have done it by now. (The would have done construction is called the conditional perfect.)

The protasis (if-clause) of such a sentence typically contains the preterite form of a verb (or the past perfect construction, for past reference), without any modal. The modal could may be used here in its role of the preterite form of can (if I could speak French). However, all the modal preterites can be used in such clauses with certain types of hypothetical future reference: if I should lose or should I lose (equivalent to if I lose); if you would/might/could stop doing that (usually used as a form of request).

Sentences with the verb wish (and expressions of wish using if only...) follow similar patterns to the if-clauses referred to above, when they have counterfactual present or past reference. When they express a desired event in the near future, the modal would is used: I wish you would visit me; If only he would give me a sign.

For more information see English conditional sentences.

Second-person singular formsedit

Early Modern English could and often did distinguish between second-person plural you (or ye) and second-person singular thou. Rather as English verbs other than modal auxiliaries agree with third-person singular subjects in today's English, in Early Modern English, verbs in general (modal auxiliaries included) agreed with a second person subject that was distinctively singular. (There was no such agreement with instances of you or ye that happened to have singular reference.) Examples from Shakespeare are shown below.