English auxiliary verbs
English auxiliary verbs are a small set of English verbs, which include the English modal verbs and a few others. Although definitions vary, as generally conceived an auxiliary lacks inherent semantic meaning but instead modifies the meaning of another verb it accompanies. In English, verb forms are often classed as auxiliary on the basis of certain grammatical properties, particularly as regards their syntax. They also participate in subject–auxiliary inversion and negation by the simple addition of "not" after them. History of the concept. In English, the adjective "auxiliary" was "formerly applied to any formative or subordinate  elements of language, e.g. prefixes, prepositions." As applied to verbs, its conception was originally rather vague and varied significantly. Some historical examples. The first English grammar, "Pamphlet for Grammar" by William Bullokar, published in 1586, does not use the term "auxiliary", but says, All other verbs are called verbs-neuters-un-perfect because they require the infinitive mood of another verb to express their signification of meaning perfectly: and be these, may, can, might or mought, could, would, should, must, ought, and sometimes, will, that being a mere sign of the future tense. (orthography has been modernized)In The life and  opinions of Tristram Shandy, (1762) the narrator's father explains that "The verbs auxiliary we are concerned in here..., are, "am"; "was"; "have"; "had"; "do"; "did"; "make"; "made"; "suffer"; "shall"; "should"; "will"; "would"; "can"; "could"; "owe"; "ought"; "used"; or "is wont"." Wiseman's grammar from 1764 notes that most verbs cannot be conjugated through all their Moods and Tenses, without one of the following principal Verbs "have" and "be". The first serves to conjugate the rest, by supplying the compound tenses of all Verbs both Regular and Irregular, whether Active, Passive, Neuter, or Impersonal, as may be seen  in its own variation, &c. It goes on to include, along with "have" and "be", "do", "may", "can", "shall", "will" as auxiliary verbs. Fowler's grammar from 1857 has the following to say:A V, or "Helping Verbs", perform the same office in the conjugation of principal verbs which inflection does in the classical languages, though even in those languages the substantive verb is sometimes used as a helping verb... The verbs that are "always auxiliary" to others are, "May", "can", "shall", "must" ";" II. Those that are "sometimes auxiliary" and sometimes principal verbs are, "Will", "have", "do", "be", and "let" .The central core that each of these agree on are the modal auxiliary verbs "may", "can", and "shall", with most including also "be", "do", and "have". Auxiliary verbs as heads. Modern grammars do not differ subtantially in the list of auxiliary verbs, though they have refined the concept and often reconceptualized auxiliary verbs as the heads of a verb phrase, rather than as a subordinate element in it. This ideas was first put forward by John Ross in 1969. Many pedagogical grammars maintain the traditional idea that auxiliary verbs are subordinate elements, but many modern grammars such as "The Cambridge  grammar of the English language" take auxiliaries to be heads. This is shown in the following tree diagram for the clause "I can swim". The clause has a subject noun phrase "I" and a head verb phrase, headed by the auxiliary verb "can". The VP also has a complement clause, which has a head VP, with the head verb "swim". Auxiliary verbs vs lexical verbs. The list of auxiliary verbs in Modern English, along with their inflected forms, is shown in the following table. Some linguists consider membership in this syntactic class the defining property for English auxiliary verbs. The  chief difference between this syntactic definition of "auxiliary verb" and the traditional definition given in the section above is that the syntactic definition includes forms of 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. In Modern English, auxiliary verbs are distinguished from lexical verbs by the NICER properties, as shown in the following table. Negation. Every case of clausal negation requires an auxiliary verb. Up until Middle English, lexical verbs could also participate in clausal negation, so a  clause like "Lee eats not apples" would have been grammatical, but this is not longer possible in Modern English. Inversion. Although English is a subject–verb–object language, there are cases where a verb comes before the subject. This is called subject-auxiliary inversion because only auxiliary verbs participate in such constructions. Again, in Middle English, lexical verbs were no different, but in Modern English "*eats Lee apples" is ungrammatical. Contraction of "not". Most English auxiliary verbs – but no lexical verbs – have a negative "-n't" morpheme. A small number of defective auxiliaries verbs don't take this morpheme. The auxiliary  may never takes this morpheme. "Am" becomes "ain't" only in non-standard English varieties; otherwise it has no negative form. Also, "will" has an irregular negative "won't" instead of the expected "*willn't" and "shall" has an irregular negative "shan't" instead of the expected (and now archaic) "*shalln't". Ellipsis. In a typical case, an auxiliary verb takes a non-finite clause complement. But this can be ellided, as in the example above. Lexical verbs taking a non-finite clause complement don't allow this kind of ellipsis. Rebuttal. When two people are arguing, the second may deny a  statement made by the first by using a stressed "too" or "so". For example, having been told that they didn't do their homework, a child may reply "I did too". This kind of rebuttal is impossible with lexical verbs. The case of "to". Various linguists, including Geoff Pullum, Paul Postal and Richard Hudson, and Robert Fiengohas have suggested that "to" in cases like "I want to go" (not the preposition "to") is a special case of an auxiliary verb with a no tensed forms. Rodney Huddleston argues against this position in "The Cambridge Grammar of the English Language", but  Robert Levine counters these proposals. BetteLou Los calls Pullum's arguments "compelling". In terms of the NICER properties, examples like "it's fine to not go" shows that it allows negation. Inversion, contraction of "not", and rebuttal would only apply to tensed forms, and "to" is argued to have none. It does allows ellipsis though: "I don't want to", but rebuttal is not possible. Auxiliaries as helping verbs. An auxiliary is traditionally understood as a verb that "helps" another verb by adding (only) grammatical information to it. On this basis, English auxiliaries include: The following are examples of sentences  containing the above types of auxiliary verbs: However, the above understanding of auxiliaries is not the only one in the literature, particularly in the case of forms of the verb "be", which may be called auxiliary even when not accompanying another verb. Other approaches to defining auxiliary verbs are described below. Auxiliaries as verbs with special grammatical behavior. A group of English verbs with certain special grammatical (syntactic) properties distinguishes them from other verbs. This group consists mainly of verbs that are auxiliaries in the above sense – verbs that add purely grammatical meaning to other verbs – and thus some authors  use the term "auxiliary verb" 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". 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: be (as infinitive, imperative and subjunctive), being and been; when used in the expression of  perfect aspect, have (as infinitive), having and had (as past participle). 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. 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: 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 typically contribute any meaning (semantic or grammatical), except when used to add emphasis to an accompanying verb. This is called the emphatic mood in English: An example would be "I do go to work on time every day" (with intonational stress placed on "do"), compared to "I go to work on time every  day." As an auxiliary, "do" mainly helps form questions, negations, etc., as described in the article on "do"-support. 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 English modal verbs, and tables summarizing their principal meaning contributions can be found in the articles Modal verb and Auxiliary verb. For more details on the uses of auxiliaries to express aspect, mood and time reference, see English clause syntax. Contracted forms. Contractions are a common feature of English, used frequently  in ordinary speech. In written English, contractions are used in mostly informal writing and sometimes in formal writing. They usually involve the elision of a vowel – an apostrophe being inserted in its place in written English – possibly accompanied by other changes. Many of these contractions involve auxiliary verbs and their negations, although not all of these have common contractions, and there are also certain other contractions not involving these verbs. Contractions were first used in speech during the early 17th century and in writing during the mid 17th century when "not" lost its stress and tone and formed the contraction  -n't. Around the same time, contracted auxiliaries were first used. When it was first used, it was limited in writing to only fiction and drama. In the 19th and 20th centuries, the use of contractions in writing spread outside of fiction such as personal letters, journalism, and descriptive texts. Certain contractions tend to be restricted to less formal speech and very informal writing, such as "John'd" or "Mary'd" for "John/Mary would" (compare the personal pronoun forms "I'd" and "you'd", which are much more likely to be encountered in relatively informal writing). This applies in particular to constructions  involving consecutive contractions, such as "wouldn't've" for "would not have". Contractions in English are generally not mandatory as in some other languages. It is almost always acceptable to use the uncontracted form, although in speech this may seem overly formal. This is often done for emphasis: "I am ready!" The uncontracted form of an auxiliary or copula must be used in elliptical sentences where its complement is omitted: "Who's ready? I am!" (not *"I'm!"). Some contractions lead to homophony, which sometimes causes errors in writing. Confusion is particularly common between "it's" (for "it is/has ) and the pronoun possessive its", and sometimes similarly between "you're" and "your". For the confusion of "have" or -"'ve" with "of" (as in "" for "would have"), see Weak and strong forms in English. Contractions of the type described here should not be confused with abbreviations, such as "Ltd." for "Limited (company)". Contraction-like abbreviations, such as "int'l" for "international", are considered abbreviations as their contracted forms cannot be pronounced in speech. Abbreviations also include acronyms and initialisms. Negative form of "am". Although there is no contraction for "am not" in standard English, there are certain colloquial or dialectal  forms that may fill this role. These may be used in declarative sentences, whose standard form contains "I am not", and in questions, with standard form "am I not?" In the declarative case the standard contraction "I'm not" is available, but this does not apply in questions, where speakers may feel the need for a negative contraction to form the analog of "isn't it", "aren't they", etc. (see below). The following are sometimes used in place of "am not" in the cases described above: There is therefore no completely satisfactory first-person equivalent to "aren't you ?" and "isn't it?" in standard English. The grammatical "am I not?" sounds stilted or affected, while "aren't I?" is grammatically dubious, and "ain't I?" is considered substandard. Nonetheless, "aren't I?" is the solution adopted in practice by most speakers. Other colloquial contractions. "Ain't" (described in more detail in the article "ain't") is a colloquialism and contraction for "am not", "is not", "was not" "are not", "were not" "has not", and "have not". In some dialects "ain't" is also used as a contraction of "do not", "does not", "did not", "cannot", "could not , will not", "would not" and "should not". The usage of "ain't" is a perennial subject of controversy in English. "Ain't" has several antecedents in English, corresponding to the various forms of "to be not" and "to have not". "An't" (sometimes "a'n't") arose from "am not" (via "amn't") and "are not" almost simultaneously. "An't" first appears in print in the work of English Restoration playwrights. In 1695 "an't" was used as a contraction of "am not", and as early as 1696 "an't" was used to mean "are not". "An't" for "is not" may have developed independently from its use  for "am not" and "are not". "Isn't" was sometimes written as "in't" or "en't", which could have changed into "an't". "An't" for "is not" may also have filled a gap as an extension of the already-used conjugations for "to be not". "An't" with a long "a" sound began to be written as "ain't", which first appears in writing in 1749. By the time "ain't" appeared, "an't" was already being used for "am not", "are not", and "is not". "An't" and "ain't" coexisted as written forms well into the nineteenth century. "Han't" or "ha'n't", an early  contraction for "has not" and "have not", developed from the elision of the "s" of "has not" and the "v" of "have not". "Han't" also appeared in the work of English Restoration playwrights. Much like "an't", "han't" was sometimes pronounced with a long "a", yielding "hain't". With H-dropping, the "h" of "han't" or "hain't" gradually disappeared in most dialects, and became "ain't". "Ain't" as a contraction for "has not"/"have not" appeared in print as early as 1819. As with "an't", "hain't" and "ain't" were found together late into the nineteenth century. Some other colloquial and dialect  contractions are described below: Contractions and inversion. In cases of subject–auxiliary inversion, particularly in the formation of questions, the negative contractions can remain together as a unit and invert with the subject, thus acting as if they were auxiliary verbs in their own right. For example: One alternative is not to use the contraction, in which case only the verb inverts with the subject, while the "not" remains in place after it: Note that the form with "isn't he" is no longer a simple contraction of the fuller form (which must be "is he not", and not *"is  not he"). Another alternative to contract the auxiliary with the subject, in which case inversion does not occur at all: Some more examples: The contracted forms of the questions are more usual in informal English. They are commonly found in tag questions. For the possibility of using "aren't I" (or other dialectal alternatives) in place of the uncontracted "am I not", see Contractions representing "am not" above. The same phenomenon sometimes occurs in the case of negative inversion: