Source: http://thehitchhikersgui.de/Modal_verb
Timestamp: 2019-04-19 07:25:42+00:00

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A modal verb is a type of verb that is used to indicate modality – that is: likelihood, ability, permission, request, capacity, suggestions, order and obligation, and advice etc. They always take base form of verb with them. Examples include the English verbs can/could, may/might, must, will/would and shall/should/ought. In English and other Germanic languages, modal verbs are often distinguished as a class based on certain grammatical properties.
An ambiguous case is You must speak Spanish. The primary meaning would be the deontic meaning ("You are required to speak Spanish.") but this may be intended epistemically ("It is surely the case that you speak Spanish.") Epistemic modals can be analyzed as raising verbs, while deontic modals can be analyzed as control verbs.
can That can indeed hinder. You can sing underwater. She can really sing.
could That could happen soon. - He could swim when he was young.
would Nothing would accomplish that. - We would eat out on Sundays.
The verbs/expressions dare, ought to, had better, and need not behave like modal auxiliaries to a large extent, although they are not productive (in linguistics, the extent commonly or frequently used) in the role to the same extent as those listed here. Furthermore, there are numerous other verbs that can be viewed as modal verbs insofar as they clearly express modality in the same way that the verbs in this list do, e.g. appear, have to, seem etc. In the strict sense, though, these other verbs do not qualify as modal verbs in English because they do not allow subject-auxiliary inversion, nor do they allow negation with not. Verbs such as be able to and be about to allow subject-auxiliary inversion and do not require do support in negatives but these are rarely classified as modal verbs because they inflect and are a modal construction involving the verb to be which itself is not a modal verb. If, however, one defines modal verb entirely in terms of meaning contribution, then these other verbs would also be modals and so the list here would have to be greatly expanded.
a. Sam may have done his homework. The modal auxiliary may is the root of the clause.
b. *Sam has may done his homework. Fails because the modal auxiliary may is not the root of the clause.
a. Jim will be helped. The modal auxiliary will is the root of the clause.
b. *Jim is will be helped. Fails because the modal auxiliary will is not the root of the clause.
Such limits in form (tense, etc.) and syntactic distribution of this class of verbs are motivation of the designation defective. Other constructions are frequently used for such a "missing" form in place of a modal, including "be able to" for can, "have to" for must, and "be going to" for shall and will (designating the future). It is of note that in this way, English modal auxiliaries are unlike modal verbs in other closely related languages; see below.
In English, main verbs but not modal verbs always require the auxiliary verb do to form negations and questions, and do can be used with main verbs to form emphatic affirmative statements. Neither negations nor questions in early modern English used to require do.
question does he work here? can he work at all?
negation + question does he not work here? can he not work at all?
(German, Afrikaans, and West Frisian never use "do" as an auxiliary verb for any function; Low Saxon and Dutch use "do" as an auxiliary, but only in colloquial speech in Dutch, whereas in Low Saxon it is of very common use, sometimes to a point where it is comparable to the way the English makes use of it).
The English modal verbs share many features and often etymology with modal verbs in other Germanic languages.
Words in the same row of the table below share the same etymological root. Because of semantic drift, however, words in the same row may no longer be proper translations of each other. For instance, the English and German verbs will are completely different in meaning, and the German one has nothing to do with constructing the future tense. These words are false friends.
In (modern) English, Afrikaans, Danish, and Swedish, the plural and singular forms are identical. For German, Dutch, Low Saxon, West Frisian, Faroese and Gothic, both a (not the) plural and a singular form of the verb are shown. Forms within parentheses are obsolete, rare, and/or mainly dialectal in the modern languages.
The English could is the preterite form of can; should is the preterite of shall; might is the preterite of may; and must was originally the preterite form of mote. (This is ignoring the use of "may" as a vestige of the subjunctive mood in English.) These verbs have acquired an independent, present tense meaning. The German verb möchten is sometimes taught as a vocabulary word and included in the list of modal verbs, but it is actually the past subjunctive form of mögen.
The English verbs dare and need have both a modal use (he dare not do it), and a non-modal use (he doesn't dare to do it). The Dutch, West Frisian, and Afrikaans verbs durven, doarre, and durf are not considered modals (but they are there, nevertheless) because their modal use has disappeared, but they have a non-modal use analogous with the English dare. Some English modals consist of more than one word, such as "had better" and "would rather".
Owing to their modal characteristics, modal verbs are among a very select group of verbs in Afrikaans that have a preterite form. Most verbs in Afrikaans only have a present and a perfect form.
Some other English verbs express modality although they are not modal verbs because they are not auxiliaries, including want, wish, hope, and like. All of these differ from the modals in English (with the disputed exception of ought (to)) in that the associated main verb takes its long infinitive form with the particle to rather than its short form without to, and in that they are fully conjugated.
Similarly, in North Germanic languages, the infinitive marker (at in Danish and Faroese, att in Swedish) is not used for main verbs with modal auxiliaries: Han kan arbejde, han kan arbeta, hann kann arbeiða (he can work). However, there also are some other constructions where the infinitive marker need not be employed, as in Swedish han försöker arbeta (he tries to work).
In many Germanic languages, the modal verbs may be used in more functions than in English. In German, for instance, modals can occur as non-finite verbs, which means they can be subordinate to other verbs in verb catenae; they need not appear as the clause root. In Swedish, some (but not all) modal verbs have infinitive forms. This for instance enables catenae containing several modal auxiliaries. The modal verbs are underlined in the following table.
(In general, there is no correspondence to the "do" constructions in other germanic languages; whence there is no question of how it is used with the modals. German, Afrikaans, and West Frisian never use "do" as an auxiliary verb for any function; Low Saxon and Dutch use "do" as an auxiliary. In Low Saxon it is of very common use, sometimes to a point where it is comparable to the way the English makes use of it).
In English, modal verbs are called defective verbs because of their incomplete conjugation: they have a narrower range of functions than ordinary verbs. For example, most have no infinitive or gerund.
Hawaiian Creole English is a creole language most of whose vocabulary, but not grammar, is drawn from English. As is generally the case with creole languages, it is an isolating language and modality is typically indicated by the use of invariant pre-verbal auxiliaries. The invariance of the modal auxiliaries to person, number, and tense makes them analogous to modal auxiliaries in English. However, as in most creoles the main verbs are also invariant; the auxiliaries are distinguished by their use in combination with (followed by) a main verb.
There are various preverbal modal auxiliaries: kaen "can", laik "want to", gata "have got to", haeftu "have to", baeta "had better", sapostu "am/is/are supposed to". Unlike in Germanic languages, tense markers are used, albeit infrequently, before modals: gon kaen kam "is going to be able to come". Waz "was" can indicate past tense before the future/volitional marker gon and the modal sapostu: Ai waz gon lift weits "I was gonna lift weights"; Ai waz sapostu go "I was supposed to go".
Hawaiian, like the Polynesian languages generally, is an isolating language, so its verbal grammar exclusively relies on unconjugated verbs. Thus, as with creoles, there is no real distinction between modal auxiliaries and lexically modal main verbs that are followed by another main verb. Hawaiian has an imperative indicated by e + verb (or in the negative by mai + verb). Some examples of the treatment of modality are as follows::pp. 38–39 Pono conveys obligation/necessity as in He pono i na kamali'i a pau e maka'ala, "It's right for children all to beware", "All children should/must beware"; ability is conveyed by hiki as in Ua hiki i keia kamali'i ke heluhelu "Has enabled to this child to read", "This child can read".
French, like some other Romance languages, does not have a grammatically distinct class of modal auxiliary verbs; instead, it expresses modality using conjugated verbs followed by infinitives: for example, pouvoir "to be able" (Je peux aller, "I can go"), devoir "to have an obligation" (Je dois aller, "I must go"), and vouloir "to want" (Je veux aller "I want to go").
Like in other Romance languages, modal verbs in Italian (verbi modali or verbi servili) together with the preterite (passato remoto) possess the perfect form (passato prossimo), where they have the peculiarity to preferably inherit the auxiliary verb from the verb they hold. Although when used alone, the auxiliary of modal verbs is always avere ("have"). Italian can use both avere ("have") and essere ("be") as auxiliaries. Modal verbs in Italian are the only group of verbs allowed to follow this particular behavior, forming so a distinct class.
For example, the perfect of potere ("can") is avere ("have"), as in ho potuto ("I could"); nevertheless, when used together with a verb that has as auxiliary essere ("be"), potere inherits the auxiliary of the second verb.
E.g.: ho visitato il castello ("I have visited the castle") / ho potuto visitare il castello ("I could visit the castle") – but: sono scappato ("I have escaped") / sono potuto scappare ("I could escape").
Italian modal verbs that follow this particular pattern are: potere ("can"), volere ("want"), dovere ("must"), sapere ("to be able to").
They must co-occur with a verb (or an understood verb).
They cannot be accompanied by aspect markers.
They cannot be modified by intensifiers such as "very".
They cannot occur before the subject.
They cannot take a direct object.
one meaning "will" or "know how to".
Spanish, like French, uses fully conjugated verbs followed by infinitives. For example, poder "to be able" (Puedo andar, "I can walk"), deber "to have an obligation" (Debo andar, "I should walk"), and querer "to want" (Quiero andar "I want to walk").
The correct use of andar in these examples would be reflexive. "Puedo andar" means "I can walk", "Puedo irme" means "I can go" or "I can take myself off/away". The same applies to the other examples.
^ Palmer, op. cit., p. 70. The subsequent text shows that the intended definitions were transposed.
^ The forms are given as in §85 and in §84 2 of Dansk grammatik (in Danish) by Niels Nielsen, Gleerups förlag, 1959, but with modernised orthography.
^ The forms are given as in §77 and in §83 h) of An introduction to modern Faroese by W. B. Lockwood, Thórshavn, 1977.
^ These first person forms are given as in §96 and in §101 of Germanische Sprachwissenschaft, II. Formenlehre (in German) by Hans Krahe, Sammlung Göschen, Band 780, 1942.
^ Krahe (op.cit., §101) treats this verb separately. He notes, that in Gothic the endings are the usual ones for the optative preterite, and assumes that this reflects the original situation. Later, he argues, in e.g. Anglo-Saxon, they were replaced by the ordinary indicative preterite forms, under influence of the preterite-present verbs proper.
^ Obsolete or dialectal, confused with and replaced by dare (OED, s.v. †tharf, thar, v. and dare, v.1).
^ Sakoda, Kent, and Jeff Siegel, Pidgin Grammar, Bess Press, 2003.
^ a b Li, Charles N., and Sandra A. Thomson, Mandarin Chinese: A Functional Reference Grammar, 1989.
Walter W. Skeat, The Concise Dictionary of English Etymology (1993), Wordsworth Editions Ltd.

References: §85
 §84
 §77
 §83
 §96
 §101
 §101
 v.