English modal auxiliary verbs
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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
- dare and need (Archaic use)
- by some accounts, do
Each of these is treated here separately.
WILL Will, is the best persons in the world
Would
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 or she would probably prefer strawberries to bananas."
Would can also be used with no modal or temporal meaning, to affect either politeness or formality of speech:
- "I would 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)
Shall
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
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 are prepared for it" (or "Should it happen, we are prepared for it"; where early Modern English would say, "If it happen, we are prepared for it," and many dialects of today would say, "If it happens, we are prepared for it").
Should commonly describes an ideal behavior or occurrence and imparts a normative meaning to the sentence; for example, "You should never lie" means roughly, "If you always behaved perfectly, you would never lie"; and "If this works, you should not feel a thing" means roughly, "I hope this will work. If it does, you will not 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 is able to be used with either a present or a future sense: "I am not sure whether he is there now; he may not be, but even if he is not, 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 is certainly not stronger" may means roughly, "While it is true that he is taller than I am, that does not make a difference, as he is certainly not stronger." (However, it may also mean, "I am not sure whether he is taller than I am, but I am sure that he is 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).
May and might do not have common negative contractions (equivalents to shan't, won't, can't, couldn't etc).
Can and could
Can is used to express ability (as in "I can speak English", meaning "I am able to speak English" or "I know how to speak English"), permission (as in "Can I use your phone?” meaning "Do you permit me to use your phone?"), willingness (as in "Can you pass me the cheese?” meaning "Please pass me the cheese"), or possibility ("There can be a very strong rivalry between siblings", meaning "There is sometimes a very strong rivalry between siblings"). (Some of these senses may be perceived as incorrect in some dialects; in particular, formal American English often prefers to use may when the sense is permission and could when the sense is willingness.) The negative of can is the single word cannot or the contraction can't.
Could has at least three distinct functions. First, it can often replace can, although generally it gives the phrase a 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 does not 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 cannot 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," does not have the same connotations as "I could go to the mall later," which suggests ability more than possibility.
Must and have to
1. Must and "Have to" are used to express that something is imperative or obligatory ("He must leave"). According to many scholars, the difference between "must" and "have to" is found in the source of the obligation.[citation needed] "Must" is said to be chosen when the obligation stems from an internal source (i.e. an obligation one imposes on oneself); "have to" when the source is external (i.e. your boss, rules, the law, an authority figure, etc). Compare "I have to finish this report today" (There is a deadline, which I did not set) with "I must finish this report today" (I am imposing my own deadline).
2. Both "Must" and "Have to" are used to express a strong belief that something is the case, but makes it clear that the speaker is not stating a fact but an opinion ("It must be here somewhere"). The basis of this belief is not factual but logical. In other words, we are speculating based on what we know about the world and how it works (i.e. what has happened in the past, someone's character, etc).
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 ought to tell him how you feel" is generally "You should not tell him how you feel," or "You had 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. Dare is especially rare in common parlance, with the notable exception of "How dare you!". "He dare not do it" is equivalent to today's "He does not/will not/would not dare to do it," while "It need not happen today" is equivalent to today's "It does not need to happen today" or "It might not happen today." However, in the sentence "I need to lose weight," need is not being used as an auxiliary since it can be conjugated to other forms: "I needed to lose weight," "I have been needing to lose weight," etc.
Do
As an auxiliary, do is essentially a "dummy"; that is, it does not 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 do not think that will happen." Also, do sometimes acts as a pro-verb: "I enjoy it, I really do [enjoy it], but I am 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).