English modal auxiliary verbs
The English modal auxiliary verbs are a subset of the English auxiliary verbs used mostly to express modality, properties such as possibility and obligation. They can most easily be distinguished from other verbs by their defectiveness and by their lack of the ending s for the third-person singular.
The central English modal auxiliary verbs are can, may, shall, will, and must. A few other verbs are usually also classed as modals: ought, and dare, and need. Use is included as well. Other expressions, notably had better, share some of their characteristics.
Modal auxiliary verbs distinguished grammatically
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 shown only if their orthography is distinctive. There are also unstressed versions that are typically, although not necessarily, written in the standard way. Where there is a blank, the modal auxiliary verb lacks this form.
Criteria for modal auxiliary verbs
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 verbs
Modal auxiliary verbs are a subset of auxiliary verbs and thus meet the criteria for these. For lists of those criteria, see the article English auxiliary verbs, but among them are that the verbs can invert with their subjects, can be negated with not, and have negative inflected forms.No untensed forms
To illustrate untensed forms, those of the irregular lexical verb take and the non-modal auxiliary verb be are the plain take and be, the gerund-participles taking and being, and the past participles taken and been.Modal auxiliary verbs lack untensed forms. Attempting to use them brings ungrammatical results:
- I will can drive if I take ten lessons.
- Canning drive would be helpful.
- I have could/canned drive since I was 18.
No subject–verb agreement
This refers to agreement of a verb with its third-person singular subject:- She can/*cans try.
Had better and used lack present tense forms. Other than in the present tense, even lexical verbs lack subject agreement and so this test is inapplicable to either had better or used.
Only a bare infinitival clause as complement
Whereas the lexical verb seem takes a to-infinitival clause, and the non-modal auxiliary verb have takes a past participial clause complement, a modal auxiliary verb can, in principle, take only a bare infinitival clause as its complement:- It can be a surprise.
- It can to be a surprise.
- It can being a surprise.
Bare infinitival clause complements are not unique to modal auxiliary verbs. Do is a non-modal auxiliary verb that takes one ; help is a lexical verb that can do so.
Ability to occur in remote apodosis
An apodosis is the "then" half of a conditional statement. 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.
Must satisfies this only for a minority of speakers, and it is questionable whether had better does so.
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....
Used does not satisfy this.
Preterite usable in the main clause for modal remoteness
- I could 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 that criterion does not apply to them. And used describes the past, not the present or future.
Comments
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
- will
- may – although the lack in today's Standard English of a negative present inflection means that it fails one of the criteria for auxiliary verbs
- shall – although the semantic divergence of shall and should means that its success with one criterion is debatable
- must – although its lack of a preterite means that it neither passes nor fails one of the criteria
Ought, dare, need, and used satisfy some of the criteria above, and are more or less often categorized as modal verbs. 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:
- 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 ; it is also used in have to, which has modal meaning, but here have only rarely follows auxiliary verb syntax;
- do, see do-support;
- to, of to-infinitival clauses.
Lists of modal auxiliary verbs
They agree that can, may, must, shall and will are, or are among, the "central modal auxiliaries", "secondary or modal auxiliaries", "modal auxiliaries", "central members of the modal auxiliary class", or "core modal verbs".
Among these five verbs, The Cambridge Grammar selects the pair can and will as "the most straightforward of the modal auxiliaries". Peter Collins agrees.
All five accord ought, need and dare a less clear or merely a marginal membership.
A Comprehensive Grammar and Warner do likewise for use; the other three deny that it is a modal auxiliary verb. For that reason, it is discussed primarily not in this article but in 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 notes, there is no variation in the status that it accords to them. Warner calls the three that he notes modal auxiliaries. Palmer says that the same three are not modal auxiliaries. Both A Comprehensive Grammar and Aarts use the term modal idiom for a choice of five. The Cambridge Grammar sees modal characteristics in all six uses of these two auxiliary verbs.
A Comprehensive Grammar calls both have got and be to modal idioms. None of the other descriptions agrees.
Palmer calls be bound/''able/going/willing to and have to semi-modals. A Comprehensive Grammar calls be able/about/apt/bound/due/going/likely/meant/obliged/supposed/willing to and have to'' semi-auxiliaries. He adds, "The boundaries of this category are not clear".
Etymology
The modals can and could are from Old English can and cuþ, which were respectively the present and preterite forms of the verb cunnan. 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 the present and preterite forms of magan ; shall and should are from sceal and sceolde, respectively the present and preterite forms of sculan ; and will and would are from wille and wolde, respectively the present and preterite forms of willan.
The aforementioned Old English verbs cunnan, magan, sculan, and willan followed the preterite-present paradigm, which explains the absence of the ending -s in the third-person present forms can, may, shall, and will.
The verb must comes from Old English moste, part of the verb motan. This was another preterite-present verb, of which moste was in fact the preterite. Similarly, ought was originally a past form—it derives from ahte, preterite of agan, another Old English preterite-present verb whose present tense form, ah, has also given the modern verb owe, and ought was formerly used as a preterite form of owe.
The verb dare also originates from a preterite-present verb, durran, specifically its present tense dear although in its non-modal uses in Modern English, it is conjugated regularly. However, need comes from the regular Old English verb neodian —the alternative third person form need, which has become the norm in modal uses, became common in the 16th century.