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Complete the sentence.
Tom doesn't like broccoli, and his sister doesn't _________________________.

The correct answer is "either" because the sentence is negative, and we use "either" after a negative verb.

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Auxiliary Verb

In English grammar, certain verb forms are classified as auxiliary verbs. Exact definitions of this term vary; an auxiliary verb is generally conceived as one with little semantic meaning of its own, which modifies the meaning of another verb with which it co-occurs. In English, verbs are often classed as auxiliaries on the basis of certain grammatical properties, particularly as regards their syntax – primarily whether they participate in subject–auxiliary inversion, and can be negated by the simple addition of not after them.

Certain auxiliaries have contracted forms, such as -'d and -'ll for had/would and will/shall. There are also many contractions formed from the negations of auxiliary verbs, ending in n't (a reduced form of not). These letter contractions can participate in inversion as a unit (as in Why haven't you done it?, where the uncontracted form would be Why have you not done it?), and thus in a certain sense can be regarded as auxiliary verbs in their own right.

An auxiliary verb is most generally understood as a verb that "helps" another verb by adding grammatical information to it. On this basis, the auxiliary verbs of English may be taken to include:

  • forms of the verb do (do, does, did), when used with other verbs to enable the formation of questions, negation, emphasis, etc.;
  • forms of the verb have, when used to express perfect aspect;
  • forms of the verb be, when used to express progressive aspect or passive voice;
  • the modal verbs, used in a variety of meanings, principally relating to modality.

The following are examples of sentences containing the above types of auxiliary verbs:

  • Do you want tea? – do is an auxiliary accompanying the verb want, used here to form a question.
  • He had given his all. – had is an auxiliary accompanying the past participle given, expressing perfect aspect.
  • We are singing. – are is an auxiliary accompanying the present participle singing, expressing progressive aspect.
  • It was destroyed. – was is an auxiliary accompanying the past participle destroyed, expressive passive voice.
  • He can do it now. – can is a modal auxiliary accompanying the verb do.

However the above understanding of auxiliary verbs is not always strictly adhered to in the literature, particularly in the case of forms of the verb be, which may be called auxiliaries even when they do not accompany another verb. Other approaches to defining auxiliary verbs are described in the following sections.

There is a group of English verbs which have certain special grammatical (syntactic) properties that distinguish them from other verbs. This group consists mainly of verbs that are auxiliaries in the above sense – verbs that add grammatical meaning to other verbs – and thus some authors use the term auxiliary verb, in relation to English, to denote precisely the verbs in this group. However, not all enumerations of English auxiliary verbs correspond exactly to the group of verbs having these grammatical properties. This group of verbs may also be referred to by other names, such as special verbs.

The principal distinguishing properties of verbs in this special group are as follows:

  • They can participate in what is called subject–auxiliary inversion, i.e. they can swap places with the subject of the clause, to form questions and for certain other purposes. For example, inversion of subject and verb is possible in the sentence They can sing (becoming Can they sing?); but it is not possible in They like to sing – it is not correct to say Like they to sing? (instead do-support is required: Do they like to sing?).
  • They undergo negation by the addition of not after them. For example, one can say They cannot sing, but not They like not to sing (again do-support is required: They don't like...).
  • Other distinct features of verbs in this group include their ability to introduce verb phrase ellipsis (I can sing can be shortened to I can in appropriate contexts, whereas I like to sing cannot be shortened to I like), and the positioning of certain adverbs directly after them (compare I can often sing with I often like to sing).

The group of verbs with the above properties consists of:

  • the finite indicative forms of the verb be: am, is, are, was, were;
  • the finite indicative forms of the verb have: have, has, had, principally when used to make perfect verb forms;
  • the finite indicative forms of the verb do: do, does, did, when used to provide do-support;
  • the principal modal verbs can, could, may, might, must, shall, should, will, would;
  • certain other verbs, sometimes but not always classed as modals: ought; dare and need in certain uses; had in had better; and sometimes used in used to (see the relevant sections of modal verbs for details).

If membership of this syntactic class is considered to be the defining property for auxiliary verbs, it is therefore the above-listed verbs that will be considered as auxiliaries.

Additionally, non-indicative and non-finite forms of the same verbs (when performing the same functions) are usually described as auxiliaries too, even though all or most of the distinctive syntactical properties do not apply to them specifically.

This concerns be (as infinitive, imperative and subjunctive), being and been; and when used in the expression of perfect aspect, have, having and had.

The chief difference between this syntactic definition of auxiliary verb and the functional definition given in the section above is that the syntactic definition includes the verb be even when used simply as a copular verb, in sentences like I am hungry and It was a cat, where it does not accompany any other verb.

Sometimes, non-auxiliary uses of have follow auxiliary syntax, as in Have you any ideas? and I haven't a clue.

Other lexical verbs do not do this in modern English, although they did so formerly, and such uses as I know not... can be found in archaic English.

Lists or sets of auxiliary verbs in English, as given by various authors, generally consist of most or all of the verbs mentioned in the above sections, though with minor discrepancies.

The main differences between the various proposed sets of auxiliary verbs are noted below.

  • For the reasons mentioned above, forms of the verb be may or may not be regarded as auxiliaries when used as a copula not accompanying any other verb.
  • The verb ought is sometimes excluded from the class of auxiliaries (specifically the modal auxiliaries) on the grounds that, unlike the principal modals, it requires the to-infinitive rather than the bare infinitive.
  • The verbs dare and need are not always considered auxiliaries (or modals); their auxiliary-like syntactic behavior (and their modal-like invariance) applies only to some instances of these verbs, e.g., dare and need.
  • The verbs had and used in the expressions had better and used to are not always included among the auxiliaries or modals; in the case of used to questions and negations are in any case more frequently formed using do-support than with auxiliary syntax.
  • Other verbs with modal-like or auxiliary-like function may sometimes be classed as auxiliaries even though they do not have auxiliary-like syntactic behavior; this may apply to have in the expression have to, meaning must.

As mentioned below, the contractions of negated forms of auxiliary verbs (isn't, shouldn't, etc.) behave in a certain sense as if they were auxiliaries in their own right, in that they can participate as a whole in subject–auxiliary inversion.

Meaning Contribution

Forms of the verbs have and be, used as auxiliaries with a main verb's past participle and present participle respectively, express perfect aspect and progressive aspect. When forms of be are used with the past participle, they express passive voice. It is possible to combine any two or all three of these uses: The room has been being cleaned for the past three hours. Here the auxiliaries has, been and being (each followed by the appropriate participle type) combine to express perfect and progressive aspect and passive voice.

The auxiliary do (does, did) does not necessarily make any meaning contribution, although it can be used to add emphasis to a clause. This is called the emphatic mood in English. An example of this use is found in "I do go to work on time every day." Also, Do does help in the formation of questions, negations, etc.

Other auxiliaries – the modal verbs – contribute meaning chiefly in the form of modality, although some of them (particularly will and sometimes shall) express future time reference. Their uses are detailed at modal verbs article, and tables summarizing their principal meaning contributions can be found in the articles on modal verb and auxiliary verb.

Adverb

An adverb is a word that modifies a verb, adjective, determiner, clause, preposition, or sentence. Adverbs typically express manner, place, time, frequency, degree, level of certainty, etc., answering questions such as how?, in what way?, when?, where?, and to what extent?. This function is called the adverbial function, and may be realized by single words (adverbs) or by multi-word expressions (adverbial phrases and adverbial clauses).

Adverbs are traditionally regarded as one of the parts of speech. However, modern linguists note that the term "adverb" has come to be used as a kind of "catch-all" category, used to classify words with various different types of syntactic behavior, not necessarily having much in common except that they do not fit into any of the other available categories (noun, adjective, preposition, etc.)

Negation

A finite indicative verb (or its clause) is negated by placing the word not after an auxiliary, modal or other "special" verb such as do, can or be. For example, the clause I go is negated with the appearance of the auxiliary do, as I do not go. When the affirmative already uses auxiliary verbs (I am going), no other auxiliary verbs are added to negate the clause (I am not going). (Until the period of early Modern English, negation was effected without additional auxiliary verbs: I go not.)

Most combinations of auxiliary verbs etc. with not have contracted forms: don't, can't, isn't, etc. (Also the uncontracted negated form of can is written as a single word cannot.) On inversion of subject and verb (such as in questions), the subject may be placed after a contracted negated form: Should he not pay? or Shouldn't he pay?

Other elements, such as noun phrases, adjectives, adverbs, infinitive and participial phrases, etc., can be negated by placing the word not before them: not the right answer, not interesting, not to enter, not noticing the train, etc.

When other negating words such as never, nobody, etc. appear in a sentence, the negating not is omitted (unlike its equivalents in many languages): I saw nothing or I didn't see anything, but not (except in non-standard speech) I didn't see nothing. Such negating words generally have corresponding negative polarity items (ever for never, anybody for nobody, etc.) which can appear in a negative context, but are not negative themselves (and can thus be used after a negation without giving rise to double negatives).

Verb

A verb is a word that expresses an action, a state, or an occurrence — and it's the engine of every English sentence. Understanding how verbs work is foundational to everything else in English grammar, from forming questions to building complex sentences.

Verb Forms

Most English verbs have five inflected forms:

  • Base form (go, write, climb) — used as an infinitive, imperative, present subjunctive, and present indicative in all persons except third-person singular.
  • -s form (goes, writes, climbs) — used for the present tense, third-person singular (she writes).
  • Past tense (went, wrote, climbed) — also called the preterite.
  • Past participle (gone, written, climbed) — identical to the past tense for regular verbs, but often different for irregular verbs.
  • -ing form (going, writing, climbing) — serves as the present participle and gerund.

The verb be is a special case with more forms than any other English verb (am, is, are, was, were, been, being). Modal verbs like can, must, and should have fewer forms than typical verbs.

Main Verbs and Auxiliaries

Verbs in English often appear in combinations: one or more auxiliary verbs paired with a main verb.

  • The dog was barking very loudly.
  • My hat has been cleaned.
  • Jane does not really like us.

The first verb in the combination is the finite verb (it carries tense and agrees with the subject). The rest are nonfinite (infinitives or participles). Notice that these verbs don't always sit next to each other — as in does not really like.

Tense, Aspect, and Mood

English expresses tense (time reference), aspect (how an action unfolds over time), and mood (the speaker's attitude toward the action) mostly through verb combinations rather than word endings. That's why you'll encounter labels like "present progressive" or "conditional perfect" — these are specific tense–aspect–mood combinations built with auxiliaries.

Self-check: If you can change the time of a sentence by swapping one word (She runs → She ran), that word is the verb.

Keep Practising

To build your verb skills from the ground up, try these challenges: Basics. "To be" in Present Tense, Basics. Common Uses of Auxiliary Verbs, and Transitive and Intransitive Verbs.

A1 | Elementary | Beginners

CEFR A1 is the first level of the Common European Framework of Reference for Languages (CEFR), a widely used standard for measuring language ability. If you're just starting to learn English — or rebuilding from scratch — this is where you begin.

What can an A1 learner do?

At A1, you can handle the most basic, everyday communication. Specifically, you're expected to:

  • Understand and use familiar everyday expressions — greetings, simple questions, common signs and instructions.
  • Introduce yourself and others — say where you live, talk about people you know, describe things you have.
  • Ask and answer simple personal questions — "What's your name?", "Where are you from?", "Do you have a car?"
  • Have short conversations — as long as the other person speaks slowly and clearly and is willing to help.

What grammar does A1 cover?

A1 focuses on the building blocks of English grammar. You'll work with:

  • Basic verb forms — the present tense of be, have, and do, plus simple regular and irregular verbs
  • Simple sentence structure — subject + verb + object word order
  • Common determiners and pronounsa, the, this, my, he, she, it
  • Basic prepositionsin, on, at, to, from
  • Simple questionsyes/no questions and wh- questions (what, where, who)
  • Everyday vocabulary and collocations — phrases that naturally go together, like make breakfast or do homework

How do you know if you're A1?

If you can read a short text like a menu or a bus sign, fill out a simple form with your personal details, and ask someone basic questions in English — you're operating at A1. If most of that still feels challenging, you're in exactly the right place.

Self-check: Try introducing yourself in five sentences — your name, where you're from, what you do, something you like, and one question for the other person. If you can do that (even with mistakes), you're solidly at A1.

What's next?

Once you're comfortable with A1 basics, you'll move toward A2, where sentences get longer, tenses expand, and you start handling more real-world situations.

To start practising, try these challenges: Are you A1/Beginner? Test your English CEFR Level!, "To be" in Present Tense, and Basics. Word Order..

Difficulty: Easy

Easy difficulty. Difficulty levels represent author's opinion about how hard a question or challenge is.