English modal auxiliary verb
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In the English language, a modal auxiliary verb is an auxiliary verb (or helping verb) that can modify the grammatical mood (or mode) of a verb. The key way to identify a modal auxiliary is by its defectiveness; the modal auxiliaries do not have participles or infinitives.
The modal auxiliaries are as follows:
- will and would
- shall and should
- may and might
- can and could
- must and have to
- ought to and had better
- in more archaic use, dare and need
- by some accounts, do
Each of these is treated here separately.
The most common use of the auxiliary will (or its contracted form 'll) is actually not modal, but temporal: it is used to indicate that an event takes place in the future, relative to the time the statement is made. For example, there is no difference in mood between "It will probably happen tomorrow" and "it probably happened yesterday"; there is only a difference in time between the two statements.
Nonetheless, perhaps as an extension of its temporal meaning, will is sometimes used with a modal sense conveying intent on the part of the speaker (in addition to certainty that the intent will be carried out):
- "You will leave now."
- "I will find a way."
It bears note that English offers other ways to express the future tense — "It's happening tomorrow", "It shall happen tomorrow", "It's going to happen tomorrow" — and that some of these can also be used with modal meaning to convey intent.
Where a main clause uses the future tense with will, adverb clauses modifying it generally use a form of the present tense:
- "I'll let you know when I've done it." (not "when I'll have done it.")
- "I'll go if I wake up in time." (not "if I'll wake up in time.")
Nonetheless, there are certain cases where a protasis (if clause) can use will. This is especially common in expressing agreements:
- "I'll go if you go" or "I'll go if you'll go."
- "I'll do it if he promises to behave" or "I'll do it if he'll promise to behave."
Will will also sometimes be used with an aspectual meaning, indicating that something is commonly the case:
- (The above sentence is an example of this.)
- "Boys will be boys."
Or, similarly, that something is likely the case, because it matches a common case, as in the sentence, "I suppose you'll be hungry, after all that running you did?"; this use, however, is no longer common in most dialects.
Finally, there are some common expressions that use the word will: "I'll say"; "I'll bet" or "I'll wager."
The auxiliary verb will originally derived from a main (non-auxiliary) verb meaning to want. This other meaning survived a long time, especially the form of to will it, and is still widely understood today; nonetheless, its use today would likely constitute an archaism.
Would is originally the past tense of will, and it (or its contracted form 'd) is still used in that sense: "In the 1960s, people thought we would all be driving hovercars by the year 2000."
Its more common use, however, is to convey the conditional mood, especially in counterfactual conditionals; that is, to express what would be the case if something were different: "If they wanted to do it, they would have done it by now." There is not always an explicit protasis ("if" clause) in this use: "Someone who likes red and hates yellow would probably prefer strawberries to bananas" means the same as, "If someone liked red and hated yellow, he would probably prefer strawberries to bananas."
Would can also be used with no modal or temporal meaning, to effect either politeness or formality of speech:
- "I'd like a glass of water, please."
- "Would you be a dear and get me a glass of water?"
- "It would seem so."
All of these uses can be described as displaying remoteness: either remoteness of time (the past), remoteness of possibility (a conditional), or remoteness of relationship to the addressee (politeness or formality).
- See also: Shall and will
Shall is used in many of the same senses as will (see above), though not all dialects use shall productively, and those that use both shall and will generally draw a distinction (though different dialects tend to draw different distinctions). In standard, perhaps old-fashioned, British English, shall in the first person, singular or plural, indicates mere intention, but in other persons shows an order, command or prophecy: "Cinderella, you shall go to the ball!" It is, therefore, impossible to make shall questions in these persons. Shall we? makes sense, Shall you? does not.
Shall derives from a main verb meaning to owe, and in dialects that use both shall and will, the former is often used in instances where an obligation, rather than an intention, is expressed.
Should is to shall as would is to will, except that should is common even in dialects where shall is not.
In some dialects, it is common to form the subjunctive mood by using should: "It is important that the law should be passed" (where other dialects would say, "It is important that the law be passed") or "If it should happen, we're prepared for it" (or "Should it happen, we're prepared for it"; where early Modern English would say something like, "If it happen, we're prepared for it," and many dialects of today would say, "If it happens, we're prepared for it").
Should commonly describes an ideal behavior or occurrence; for example, "You should never lie" means roughly, "If you always behaved perfectly, you would never lie"; and "If this works, you shouldn't feel a thing" means roughly, "I hope this will work. If it does, you won't feel a thing." In dialects that use shall commonly, however, this restriction does not apply; for example, a speaker of such a dialect might say, "If I failed that test, I think I should cry," meaning the same thing as, "If I failed that test, I think I would cry."
May and might
May is used to indicate permission ("May I have a word with you?") or possibility ("That may be."), though in some dialects, the former use is often supplanted by can (see below), and the latter by might (which was originally its past tense), making this auxiliary rather uncommon in those dialects.
May can be used with either a present or a future sense: "I'm not sure whether he's there now; he may not be, but even if he isn't, he may go there later." Theoretically speaking, might is the corresponding past-tense form, but since some dialects use might quite commonly with a present or future sense, it is more common to use may or might with the perfect aspect to provide a past sense: "He might have been gone when we got there, or he might have been hiding."
May is also used to express irrelevance in spite of certain or likely truth: "He may be taller than I am, but he's certainly not stronger" may means roughly, "While it's true that he's taller than I am, that doesn't make a difference, as he's certainly not stronger." (However, it may also mean, "I'm not sure whether he's taller than I am, but I am sure that he's not stronger.") In many dialects, might is used in this sense as well.
In addition to what has already been mentioned, might also serves as the conditional mood of may: "If he were more polite, he might be better liked." Also, while there are some dialects where the use of might to replace may is very common, even in colloquial or informal speech, there are other dialects where might serves a more polite or formal form of may, just as would does for will (see above) and could does for can (see below).
Can and could
Can is used to express ability ("I can speak English," meaning "I am able to speak English" or "I know how to speak English") or, in some dialects, permission or willingness ("Can I use your phone?", meaning "Do I have your permission to use your phone?"; "Can you pass me the cheese?" meaning "Are you willing to pass me the cheese?" or "Please pass me the cheese"). It is also used to express a general possibility ("There can be a very strong rivalry between siblings," meaning "There is sometimes a very strong rivalry between siblings"). The negative of can is the single word cannot (or can't).
Could has at least three distinct functions. First, it can often replace can, although generally it gives the phrase a more conditional tone. For example, "I can help you with your work" suggests that the speaker is ready and willing to help, whereas "I could help you with your work" gives a more tentative sense of ability to help. In this sense, could is often used like a conditional: "I could help you if you helped yourself."
Second, could functions as a kind of past tense for can, though could doesn't function grammatically like any regular past simple verb.
Third, could carries the same meaning as might or may in the present. That is, could suggests that something is a possibility. For instance, John is not in the office today, he could be sick. In this phrase, might or may would carry the same meaning. Note that can in the negative carries the same idea as couldn't in this sense: "He can't have left already; why would he want to get there so early?" Also note that when regarding potential futures actions could is not equivalent to might or may. "I might go to the mall later," doesn't have the same connotations as "I could go to the mall later," which suggests ability more than possibility.
Must and have to
Must is used to express that something is imperative or obligatory ("He must leave"), or that something is certain ("It must be here somewhere"). Have to is synonymous with must.
Ought to and had better
Ought to and had better are synonymous with one of the senses of should: it is used to express an ideal behavior or occurrence or suggested obligation. In dialects that use shall commonly, should has a wide array of meanings, so ought is very common (as it is more precise), as is ought not (or oughtn't). In other dialects, ought may or may not be common, but ought not is generally quite rare: the opposite of "You oughtta tell him how you feel" is generally "You shouldn't tell him how you feel," or "You'd better not tell him how you feel." There is no negative contraction for had better. Had better not is used at all times. In speech, the had in had better is generally disregarded.
Dare and need
Nowadays, dare and need are not commonly used as auxiliaries, but formerly, both were. "He dare not do it" is equivalent to today's "He doesn't/won't/wouldn't dare to do it," while "It need not happen today" is equivalent to today's "It doesn't need to happen today" or "It might not happen today." Nonetheless, need as an auxiliary is still somewhat in use today, while dare is now quite rare. Need as a modal is quite common in American English when used in the positive form and acts like the modals must and have to (eg. I need to lose weight/I must lose weight/I have to lose weight), but is almost never used in the negative form.
As an auxiliary, do is essentially a "dummy"; that is, it doesn't generally affect the meaning. It is used to form questions and negations when no other auxiliary is present: "I don't want to do it." It is also sometimes used for emphasis: "I do understand your concern, but I don't think that will happen." Also, do sometimes acts as a pro-verb: "I enjoy it, I really do [enjoy it], but I'm not good at it." (Other auxiliaries do this as well: "I can do it, I really can [do it], it just takes me longer"; but it bears particular note that in the case of do, it is often used as a pro-verb when it would be absent if the verb were present.) Because it does not affect the meaning of its verb, not all grammarians acknowledge do as a modal auxiliary. In a sense, it indicates a lack of modal auxiliary. (Do is also different in that it has a distinct third-person singular form, does, and in that its past tense, did, is used exactly as a past tense, not as a more general remote form.)
- Modal verb
- Verbs in English Grammar, wikibook