Topic 20 – Auxiliary and modal verbs: Forms and functions

Topic 20 – Auxiliary and modal verbs: Forms and functions

Throughout this topic I am going to deal with auxiliary verbs. I will begin by having a look at the general features of auxiliaries and establishing a difference between primary and modal auxiliaries. Then I will analyse the three primary auxiliaries, DO, BE and HAVE. Finally, in my last section I will present the characteristics of modal verbs and will analyse each of the modals separately.

Two major verb classes, lexical and auxiliary verbs, are said to work together at sentence level. Lexical verbs constitute the principal part of the verb phrase (play, believe, go…) and may or may not be accompanied by auxiliaries (Ana Obregón comes tomorrow / Ana Obregón may visit me tomorrow). Auxiliary verbs are defined as those closed class verbal items which help ordinary verbs form a tense or an expression, for example, by combining with present or past participles or with infinitive. Auxiliary verbs can be classified into two categories:

  • Primary auxiliaries: DO, HAVE and BE.
  • Modal auxiliaries: CAN, COULD, MAY, MIGHT, MUST, SHALL, SHOULD, OUGHT TO and WILL.

We also find the so called marginal modals or semi-modals: DARE, NEED and USED TO. They are so called because they can be used both as auxiliaries and as lexical verbs (He needn’t be careful/ He needs to be careful).

Let’s see some of the features of auxiliary verbs, both primary and modal:

  • Operator in negation with “not”: in forming negative finite clauses, the first auxiliary is placed before the negative word NOT.

She cannot do it / She saw not it*

Full verbs are distinguished from auxiliaries by their inability to form negation in this way. They require the use of the auxiliary DO.

  • Inversion of subject and operator: auxiliaries, as operators, admit inversion, that is, the subject noun phrase and the auxiliary (the first one if there are two or more) change places, especially in interrogative clauses.

She will come / Will she come?

She plans to come / Plans she to come?*

The same as with NOT negation, main verbs require the use of DO to form interrogative clauses.

Inversion of subject and operator occurs not only in interrogatives, but also in sentences with introductory negatives or semi-negatives.

At no time is Ana left unguarded

  • Operator in reduced clauses: the reply to a question such as “Can you drive a car?” may be the complete form “No, I can’t drive a car”, but a more likely reply would be the elliptical construction “No, I can’t”. Two types of reduced constructions containing an operator without a main verb are:
    • So / neither / nor + operator. Bisbal will sing and so will Chenoa
    • Operator + too / either. Papuchi was a great man and Julio is too

Do is used as an empty operator where the clause has no other auxiliary.

  • There is the possibility of construction with existential THERE.

There will be a great scandal about Camilla’s anniversary

There speak a lot about the scandal*

  • No imperative form is realized by these forms, since they are not lexical verbs. Can!* Be!*

After this section dealing with the classification and main features of auxiliary verbs, I am going to move on to my second section, in which I will analyse the primary auxiliary verbs. The primary auxiliaries, when used as auxiliaries, require a participle or an infinitive in order to have full meaning. However, when used as ordinary verbs they are the only verb in the sentences.


Be is constructed as an auxiliary even when it functions as a main verb. For example, it normally has no do-construction, except with negative and persuasive imperatives.

Don’t be silly / Do be quiet

The auxiliary BE has two functions: aspect auxiliary and passive auxiliary. It is the only verb in English that has 8 different forms: be, being, been, am, is, are, was, were. Let’s see which its main meanings are:

  • When a form of the verb BE is combined with the present participle of another verb, it functions as an auxiliary in the formation of the progressive tenses. Beckham is lying Victoria about his love affairs.
  • When it is combined with the past participle of another verb, it forms the passive voice. Michael Jackon was arrested after abusing a child
  • To express an immediate future, this verb can be used in two constructions: in the verbal form BE GOING TO + INFINITIVE or in periphrasis such as BE ABOUT TO / ON THE POINT OF.

Athina Onassis is going to buy a new island

  • The construction BE TO + INFINITIVE is similar in meaning to “have to” and “ought to”. Posh Victoria is to return to England


Like BE, HAVE is both a main verb and an auxiliary. As a main verb, it means “possess”, and is sometimes constructed as an auxiliary, especially in BrE. AmE prefers the do-construction.

Karina hasn’t any money (BrE)

Karina doesn’t have any money (AmE)

The auxiliary HAVE combines with past participle to form perfective complex verb phrases. In this sense, it is with tenses that are formed with HAVE: present perfect and past perfect.


DO also can be both an auxiliary and a main verb. As an auxiliary, DO has two non-finite forms: present and past forms (DO / DID). All uses of DO as an auxiliary are termed as do-support or do-periphrasis. This applies to the use of DO as an empty or dummy operator in conditions where the construction requires an operator, but where there is no semantic reason for any other operator to be present. The main constructions are:

  • In indicative clauses negated by NOT, where the verb is in simple present or past. The President didn’t want to resign

Negative imperative clauses introduced by DO NOT or DON’T may be placed in the same category.

  • In questions and other constructions involving subject-operator inversion, where the verb is in the simple present or past tense.

Did Rociito stay late?

This category includes tag questions and other reduced questions where the dummy operator is not accompanied by the main verb. It also includes inversion after an initial negative.

I don’t like him, do you? Never did he help me

  • In emphasis or persuasive constructions where the verb is in the simple present or past. The manager does want to see you.
  • In reduced clauses, where DO acts as a dummy operator preceding ellipsis of a predication. You speak faster than I do.

Up to this point I have looked at the general characteristics of the auxiliary verbs and have dealt with primary auxiliary verbs. Now I am going to move on to deal with modal verbs. Modals express an attitude to what we say. The modality function reflects the speaker’s judgement of the likelihood of a proposition to be true and it is divided into two types: modals expressing permission, obligation, volition, willingness, etc, which involve some kind of intrinsic human control over events; and modals meaning possibility, necessity and prediction, which involve human judgement of what it is or it is not likely to happen.

Apart from the characteristics of auxiliary verbs I mentioned in my first section, modal verbs have a set of distinguishing features:

· Modal verbs are followed by the base form of the verb or by the base form BE / HAVE + past participle.

Brad Pitt may adopt Angelina’s children

Jeniffer might have found a new boyfriend

· Modal verbs do not inflect, that is, they do not take an –s in the third person or –ing or –ed.

· Modal verbs do not take the auxiliary DO. The negative is formed by adding NOT. You can’t go in Pacha if you aren’t beautiful

· Modal verbs have no infinitive. Other expressions must be used instead.

(Can) Will you be able to help me?

(Must) I’m going to have to leave

  • Modal verbs have no past form, and other expressions must be used instead. There are some exceptions, as some authors consider COULD the past of CAN.

(Must) I had to change the tyre

(Can) Were you able to find the disco?

After seeing what the main features of modal verbs are, I am going to move on to deal with each modal verb separately.

CAN expresses:

  • Present ability and awareness. It may be paraphrased by using the “be able to” construction. This construction will be used with WILL, GOING TO, USED TO…

Kofi Annan can speak 17 languages

Kofi Annan is able to speak 17 languages

  • Permission: can expresses permission, and it is less formal than “may”.

Can I smoke within the office?

  • Theoretical possibility: the number of deaths out of cancer can be reduced if smoking is banned

COULD expresses:

  • Past ability: The Pope could read 11 languages
  • Present or future permission: Could I spend all my money in sweets, daddy?
  • Present possibility, theoretical or factual: Alonso could win the world cup next year again
  • Contingent possibility or ability in unreal conditions: Underdeveloped countries could improve if the rich countries would condone their debts

MAY / MIGHT express:

  • Permission: “May” and “might” can be both used to ask for permission. They are more formal than “can” and “could”. “Might” is very polite and formal; it is not as common as “may”. Instead of MAY NOT, the stronger MUSTN’T is often used in the negative to express prohibition.

May I continue delivering my speech?

You may not / mustn’t copy in the exam

  • Possibility, usually factual: We often use “may” and “might” to say that there is a chance that something is true, or that there is a possibility of it happening. Both “may” and “might” are used to talk about the present or future. “Might” is mostly used as a less definite or more hesitant form of “may”, suggesting a smaller chance -it is used when people think that something is possible but not very likely.

David Beckham may go to London (perhaps a 50% chance).

Victoria of Spice Girls might spend a couple of weeks helping in Ethiopia (perhaps a 20% chance in the best of scenarios).

  • There is a rare use of MAY as a “quasi-subjunctive” auxiliary, for instance, to express wish, normally in positive sentences.

May the Liverpool lose all the matches!!

SHALL expresses:

  • Willingness on the part of the speaker in second and third person. It is always associated with promises and threats.

You shall do as you wish

  • Intention on the part of the speaker, only in the first person. This is the only meaning widely used today.

I shall go to Stratford-upon-Avon in order to continue with my Shakespearean


  • We use this modal as a substitute for the future use of “will” in formal style with a first person subject.
  • Insistence on the part of the speaker, with a restricted use. You shall do as I say
  • Legal or quasi-legal injunction. The vendor shall maintain the equipment in good maintain.
  • In questions, we use shall to ask for suggestions and instructions.

What shall we drink?

SHOULD expresses:

  • Obligation and logical necessity: We often use “should” to talk about obligation, duty and similar ideas. It is less strong than “must” and with the perfective aspect, “should” and “ought to” typically have the stronger implication that the recommendation has not been carried out.

I should have phoned The National Trust this morning, but I forgot.

  • In questions, “should” is used to ask for advice or instructions

Blimey! I’ve lost my ID card. Should I go and see the police, do you think?

  • Putative use after certain expressions: It’s a pity that…, I’m surprised that…

It’s odd that you should say that to me

  • Contingent use in first person only, similar to would.

I should learn Russian if I had the chance

  • In rather formal real conditions. If you should change your mind, please let me know.


Will expresses:

  • Willingness, used in polite requests.

Will you please stop smoking?

  • Intention, usually with WILL in the contracted form (‘LL) and mainly in the first person. I’ll learn German as soon as I pass my English exam
  • Insistence (Will is stressed and there is no contraction)

He will do it, no matter what you say

  • Prediction: will has the similar meaning of other expressions for logical necessity and habitual present.

· Specific prediction. The game will / must / should be finished by now

· Timeless prediction. Oil will float / float on water

· Habitual prediction. He’ll (always) talk for hours if you give him the chance

Would expresses:

  • Willingness: Would you excuse me?
  • Insistence: It’s your fault; you would take the baby with you.
  • Characteristic activity in the past: When Bono was much younger, he would sing in dingy Irish pubs.
  • Contingent use in the main clause of a conditional sentence:

He would smoke too much if I didn’t stop him

  • Probability: That would be his mother

MUST expresses:

  • Obligation or compulsion in the present tense. In the past, we use HAD TO instead of MUST, except in reported speech.

Candidates must deliver their speeches without any notes.

There are two negatives:

· Needn’t and don’t have to, whose meaning is “not be obliged to”

You needn’t come if you don’t want to

· Mustn’t, whose meaning is “be obliged not to”

You mustn’t use your dictionaries during the exam

· Logical necessity. Must” denotes near certainty, arrived at as the result of inference or reasoning.

It must have been love, but it’s over now

In sentences with interrogative or negative meaning, CAN’T is used instead of MUST It can’t have been love.

OUGHT TO expresses:

· Obligation. You are bleeding too much. You ought to go to the doctor.

· Logical necessity or expectation. They ought to be here by now

After analysing each of the modal auxiliaries, I am going to move on to the last section of this topic, in which I will have a look at marginal modal auxiliaries.

USED is always followed by a TO infinitive. In the negative, it takes a do-construction, in which case we find two possible spellings: didn’t use to and didn’t used to. Moreover, in the interrogative there are also two constructions: “used he to…?” (BrE), and “did he use to…?”, preferred both in AmE and BrE.

DARE and NEED can be constructed either as modal auxiliaries (with bare infinitive and with no inflected –s form) or as lexical verbs (with to-infinitive and with inflected –s form). The modal verb construction is restricted to non-assertive contexts, that is, mainly negative and interrogative sentences, whereas the lexical verb construction can always be used and is in fact the most common. DARE and NEED as auxiliaries are probably rarer in AmE than in BrE.

To sum up, throughout this topic I have talked about auxiliary verbs. I began by having a look at the general features of auxiliaries and establishing a difference between primary and modal auxiliaries. Then I have analysed the three primary auxiliaries, DO, BE and HAVE. Finally, in my last section I have presented the characteristics of modal verbs and have analysed each of the modals separately.