An auxiliary verb ( abbreviated ) is a

verb A verb is a word that generally conveys an action (''bring'', ''read'', ''walk'', ''run'', ''learn''), an occurrence (''happen'', ''become''), or a state of being (''be'', ''exist'', ''stand''). In the usual description of English, the basic f ...

that adds functional or grammatical meaning to the

clause In language, a clause is a Constituent (linguistics), constituent or Phrase (grammar), phrase that comprises a semantic predicand (expressed or not) and a semantic Predicate (grammar), predicate. A typical clause consists of a subject (grammar), ...

in which it occurs, so as to express tense, aspect, modality,

voice The human voice consists of sound made by a human being using the vocal tract, including talking, singing, laughing, crying, screaming, shouting, humming or yelling. The human voice frequency is specifically a part of human sound produ ...

, emphasis, etc. Auxiliary verbs usually accompany an infinitive verb or a

participle In linguistics, a participle (; abbr. ) is a nonfinite verb form that has some of the characteristics and functions of both verbs and adjectives. More narrowly, ''participle'' has been defined as "a word derived from a verb and used as an adject ...

, which respectively provide the main semantic content of the clause. An example is the verb ''have'' in the sentence ''I have finished my lunch.'' Here, the auxiliary ''have'' helps to express the

perfect aspect The perfect tense or aspect ( abbreviated or ) is a verb form that indicates that an action or circumstance occurred earlier than the time under consideration, often focusing attention on the resulting state rather than on the occurrence itself. ...

along with the participle, ''finished''. Some sentences contain a chain of two or more auxiliary verbs. Auxiliary verbs are also called helping verbs, helper verbs, or (verbal) auxiliaries. Research has been conducted into split inflection in auxiliary verbs.

Basic examples

Below are some sentences that contain representative auxiliary verbs from English, Spanish, German and French, with the auxiliary verb marked in bold: ::a. Do you want tea? – ''do'' is an auxiliary accompanying the infinitive, ''want'', used here to form a question – see ''do''-support. ::b. She has given her best shot. – ''have'', from which ''has'' is

inflected In linguistic Morphology (linguistics), morphology, inflection (less commonly, inflexion) is a process of word formation in which a word is modified to express different grammatical category, grammatical categories such as grammatical tense, ...

, is an auxiliary used in expressing the

of ''give''. ::c. He cogido tu lápiz. – ''he'' is an auxiliary accompanying the infinitive ''coger'', used here to form a verb phrase, the perfect present in Spanish. :::(I) have grabbed your pencil = 'I have taken your pencil.' ::d. Das wurde mehrmals gesagt. – ''werden'', from which ''wurde'' is inflected, ''become'' is an auxiliary used to build the

passive voice A passive voice construction is a grammatical voice construction that is found in many languages. In a clause with passive voice, the grammatical subject expresses the ''theme'' or ''patient'' of the main verb – that is, the person or thing ...

in German. :::That became many times said = 'That was said many times.' ::e. Sie ist nach Hause gegangen. – ''sein'', from which ''ist'' is inflected, 'be' is an auxiliary used with movement verbs to build the perfect tense/aspect in German. :::She is to home gone = 'She went home/She has gone home.' ::f. Jai vu le soleil. – ''avoir'', from which ''ai'' is inflected, 'have' is an auxiliary used to build the perfect tense/aspect in French. :::I have seen the sun = 'I have seen the sun/I saw the sun.' ::g. Nous sommes hébergés par un ami. – ''être'', from which ''sommes'' is inflected, 'be' is an auxiliary used to build the passive voice in French. :::We are hosted by a friend. These auxiliaries help express a question, show tense/aspect, or form passive voice. Auxiliaries like these typically appear with a full verb that carries the main semantic content of the clause.

Traits across languages

Auxiliary verbs typically help express grammatical tense, aspect, mood, and

. They generally appear together with an infinitive. The auxiliary is said to "help" the infinitive. The auxiliary verbs of a language form a closed class, i.e., there is a fixed, relatively small number of them. Widely acknowledged verbs that can serve as auxiliaries in English and many related languages are the equivalents of ''be'' to express passive voice, and ''have'' (and sometimes ''be'') to express

or past time reference. In some treatments, the copula ''be'' is classed as an auxiliary even though it does not "help" another verb, e.g., ::The bird is in the tree. – ''is'' serves as a copula with a

predicative expression A predicative expression (or just predicative) is part of a clause predicate, and is an expression that typically follows a copula or linking verb, e.g. ''be'', ''seem'', ''appear'', or that appears as a second complement (object complement) of ...

not containing any other verb. Definitions of auxiliary verbs are not always consistent across languages, or even among authors discussing the same language. Modal verbs may or may not be classified as auxiliaries, depending on the language. In the case of English, verbs are often identified as auxiliaries based on their grammatical behavior, as described below. In some cases, verbs that function similarly to auxiliaries, but are not considered full members of that class (perhaps because they carry some independent lexical information), are called ''semi-auxiliaries''. In French, for example, verbs such as ''devoir'' (have to), ''pouvoir'' (be able to), ''aller'' (be going to), ''vouloir'' (want), ''faire'' (make), and ''laisser'' (let), when used together with the infinitive of another verb, can be called semi-auxiliaries. There has also been a study on auxiliary verb constructions in Dravidian languages.

English

The following sections consider auxiliary verbs in English. They list auxiliary verbs, then present the diagnostics that motivate this special class (subject-auxiliary inversion and negation with ''not''). The modal verbs are included in this class, due to their behavior with respect to these diagnostics.

List of auxiliaries in English

A list of verbs that (can) function as auxiliaries in English is as follows: ::''be'', ''can'', ''could'', ''dare'', ''do'', ''have'', ''may'', ''might'', ''must'', ''need'', ''ought'', ''shall'', ''should'', ''will'', ''would'' The status of ''dare (not)'', ''need (not)'', and ''ought (to)'' is debatable and the use of these verbs as auxiliaries can vary across dialects of English. If the negative forms ''can't'', ''don't'', ''won't'', etc. are viewed as separate verbs (and not as contractions), then the number of auxiliaries increases. The verbs ''do'' and ''have'' can also function as full verbs or as light verbs, which can be a source of confusion about their status. The modal verbs (''can'', ''could'', ''may'', ''might'', ''must'', ''shall'', ''should'', ''will'', ''would'', and ''dare'', ''need'' and ''ought'' when included) form a subclass of auxiliary verbs. Modal verbs are defective insofar as they cannot be

, nor do they appear as gerunds, infinitives, or participles. The following table summarizes the auxiliary verbs in standard English and the meaning contribution to the clauses in which they appear. Many auxiliary verbs are listed more than once in the table based upon discernible differences in use. Deontic modality expresses an ability, necessity, or obligation that is associated with an agent subject. Epistemic modality expresses the speaker's assessment of reality or likelihood of reality. Distinguishing between the two types of modality can be difficult, since many sentences contain a modal verb that allows both interpretations.

List of auxiliaries unique to African American Vernacular English

African American Vernacular English makes a variety of finer tense/aspect distinctions than other dialects of English by making use of unique variant forms of, in particular: habitual 'be', reduced 'done' (dən), and stressed 'been' (BIN):

Diagnostics for identifying auxiliary verbs in English

The verbs listed in the previous section can be classified as auxiliaries based upon two diagnostics: they allow subject–auxiliary inversion (the type of inversion used to form questions etc.) and (equivalently) they can take ''not'' as a postdependent (a dependent that follows its

head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple ani ...

). The following examples illustrate the extent to which subject–auxiliary inversion can occur with an auxiliary verb but not with a full verb. (The asterisk * is the means commonly used in linguistics to indicate that the example is grammatically unacceptable or that a particular construction has never been attested in use). ::a. He was working today. ::b. Was he working today? - Auxiliary verb ''was'' allows subject–auxiliary inversion. ::a. He worked today. ::b. *Worked he today? - Full verb ''worked'' does not allow subject–auxiliary inversion. ::a. She can see it. ::b. Can she see it? - Auxiliary verb ''can'' allows subject–auxiliary inversion. ::a. She sees it. ::b. *Sees she it? - Full verb ''sees'' does not allow subject–auxiliary inversion. The following examples illustrate that the negation ''not'' can appear as a postdependent of a finite auxiliary verb, but not as a postdependent of a finite full verb: ::a. Sam would try that. ::b. Sam would not try that. - The negation ''not'' appears as a postdependent of the finite auxiliary ''would''. ::a. Sam tried that. ::b. *Sam tried not that. - The negation ''not'' cannot appear as a postdependent of the finite full verb ''tried''. ::a. Tom could help. ::b. Tom could not help. - The negation ''not'' appears as a postdependent of the finite auxiliary ''could''. ::a. Tom helped. ::b. *Tom helped not. - The negation ''not'' cannot appear as a postdependent of the finite full verb ''helped''. A third diagnostic that can be used for identifying auxiliary verbs is verb phrase ellipsis. See the article on

verb phrase ellipsis In linguistics, Verb phrase ellipsis (VP ellipsis or VPE) is a type of Ellipsis (linguistics), grammatical omission where a verb phrase is left out (elided) but its meaning can still be inferred from context. For example, "''She will sell sea shell ...

for examples. These criteria lead to the copula ''be'' and non-copular use of ''be'' as an existential verb being considered an auxiliary (it undergoes inversion and takes postdependent ''not'', e.g., ''Is she the boss?'', ''She is not the boss'', ''Is there a God?'', ''There is a God''). However, if one defines ''auxiliary verb'' as a verb that somehow "helps" another verb, then the copula ''be'' is not an auxiliary, because it appears without another verb. The literature on auxiliary verbs is somewhat inconsistent in this area. There are also some properties that some but not all auxiliary verbs have. Their presence can be used to conclude that the verb is an auxiliary, but their absence does not guarantee the converse. One such property is to have the same form in the present tense, also for the first and the third person singular. This in particular is typical for '' modal'' auxiliary verbs, such as ''will'' and ''must''. (Examples: ''He will come tomorrow'', ''she must do it at once'', not ~~''he wills''~~ or ~~''she musts''~~.)

Light verbs

Some syntacticians distinguish between auxiliary verbs and light verbs. The two are similar insofar as both verb types contribute mainly just functional information to the clauses in which they appear. Hence both do not qualify as separate predicates, but rather they form part of a predicate with another expression – usually with a full verb in the case of auxiliary verbs and usually with a noun in the case of light verbs. In English, light verbs differ from auxiliary verbs in that they cannot undergo inversion and they cannot take ''not'' as a postdependent. The verbs ''have'' and ''do'' can function as auxiliary verbs or as light verbs (or as full verbs). When they are light verbs, they fail the inversion and negation diagnostics for auxiliaries, e.g. Note that in some dialects (for example, the West and South West dialects of

Hiberno-English Hiberno-English or Irish English (IrE), also formerly sometimes called Anglo-Irish, is the set of dialects of English native to the island of Ireland. In both the Republic of Ireland and Northern Ireland, English is the first language in e ...

), the inversion test may sound correct to native speakers. ::a. They had a long meeting. ::b. *Had they a long meeting? - Light verb ''had'' fails the inversion test. ::c. *They had not a long meeting. - Light verb ''had'' fails the negation test. ::a. She did a report on pandering politicians. ::b. *Did she a report on pandering politicians? - Light verb ''did'' fails the inversion test. ::c. *She did not a report on pandering politicians. - Light verb ''did'' fails the negation test. (In some cases, though, ''have'' may undergo auxiliary-type inversion and negation even when it is not used as an auxiliary verb – see .) Sometimes the distinction between auxiliary verbs and light verbs is overlooked or confused. Certain verbs (e.g., ''used to'', ''have to'', etc.) may be judged as light verbs by some authors, but as auxiliaries by others.Jurafsky and Martin (2000:22), for instance, lists ''have'' as a modal auxiliary when it appears as ''have to'' and Fowler's Modern English Usage (1996:195) lists ''used to'' as a "marginal modal".

Notes

References

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