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Auxiliary verb
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Auxiliary verb

Auxiliary verbs are, loosely, verbs that specify more about the main verb that follows. For English auxiliary verbs, the specified 'more' alters the basic form of the main verb to have one or more of the following functions: Passive, Progressive, Perfective, Modal, and Dummy.

Table of contents
1 Introduction
2 Functions of the English Auxiliary Verb
3 Properties of the English Auxiliary Verb
4 Other Languages
5 See also
6 Reference


In stricter linguistic terms than the simple definition above, the following is true:

A point to note is that a finite verb consists of more than one word if there is one or more auxiliary verbs (e.g. "write" - just a full verb, "have written" - full verb plus one auxiliary, "have been written" - full verb plus two auxiliaries). Another important point is that an auxiliary verb is a syntactic concept, i.e. whether a verb is an auxiliary verb depends on its function within the sentence. In particular, be, have, and do can be either full verbs or auxiliaries; they are auxiliaries in: where the full verb is write, and they are full verbs themselves in: Finally, it should be remembered that the functions of the English auxiliary verb below can be combined (as in this sentence where "should be remembered" contains a modal "should" and a passive "be").

Functions of the English Auxiliary Verb


The verb be is used in the passive form to express an action where the subject is unknowable, not known, or of less interest than the action itself, e.g. the window is broken. (See also Grammatical voice.)


This form, also known as the continuous form, uses the verb be. It is used to express the speaker's interpretation of the temporal nature of the event, e.g. I am doing my homework. (See also Grammatical aspect.)


The verb have is used in the perfective form to look back, i.e. retrospectively, at a past action from the present time. Or in other words, it is used to express an action that still has relevance to the present, e.g. Peter has fallen in love. (See also Grammatical aspect.)


There are nine modal verbs: can/could, may/might, shall/should, will/would and must. They differ from the other auxiliaries both in that they are defective verbs, and in that they can never function as main verbs. They express the speaker's (or listener's) judgement or opinion at the moment of speaking. Some of the modal verbs have been seen as a conditional tense form in English.

Some schools of thought consider could to represent the past tense of can. However, according to Michael Lewis, (The English Verb), this is not always true. "Could I get you something?", clearly is not expressing Past Time. Lewis instead suggests that could is a remote form of can. It is evident after re-examining the usage of could in this light, that remoteness does describe the general meaning, e.g.

The remaining modal auxiliaries can be viewed in this same manner. Lewis covers this area in detail in his book, see reference.


Because only auxiliaries can be inverted to form questions and only auxiliaries can take negation directly, a dummy auxiliary do is used for questions and negatives when only a full verb exists in the positive statement (i.e. there are no auxiliaries in the positive, non-interrogative form). The same dummy do is used for emphasis in the positive statement form.

For example, if the positive statement form is:

the interrogative, negative and emphatic forms are respectively: Compare this with:


English contains many verb phrases that function as quasi-auxiliaries, such as be going to, used to, is about to. These quasi-auxiliaries require an infinitive. Others, such as need (as in need fixing), take a present participle, while yet others such as get as in get broken take a past participle.

Properties of the English Auxiliary Verb


Auxiliaries take not (or n't) to form the negative, e.g. can't, won't, shouldn't, etc. In certain tenses, in questions, when a contracted auxiliary verb can be used, the position of the negative particle n't moves from the main verb to the auxiliary: cf. Does it not work? and Doesn't it work?

See English verbs


Auxiliaries invert to form questions:


The dummy auxiliary do is used for emphasis in positive statements (see above):

I do like this beer!


Auxiliaries can appear alone where a main verb has been omitted, but is understood:

John never sings, but Mary does [sing].


Other Languages

Some languages use "be" for the perfective forms of some or all verbs, instead of "have" (in Esperanto, for example, Mi estis irinta = I was having-gone = I had gone). French, German, and Dutch use it for verbs of motion and becoming, and (in German and Dutch) for "to be" itself, as does Italian. The use of auxiliaries is one variation among Romance languages. Finnish uses ole for all verbs: "Sillä niin on Jumala maailmaa rakastanut" (Because so much is God the world loved). English uses "be" only with "go" in some senses.

See also


The English Verb 'An Exploration of Structure and Meaning', Michael Lewis. Language Teaching Publications. ISBN 0 906717 40 X