What Are Auxiliary Verbs

In English grammar, an auxiliary verb is a verb that determines the mood, tense, voice,  or aspect of another verb in a verb phrase. Auxiliary verbs include be, do, and have along with modals such as can, might, and will and can be contrasted with main verbs  and  lexical verbs. Auxiliaries are also called helping verbs because they help to complete the meaning of main verbs. Unlike main verbs, auxiliary verbs cant be the only verb in a sentence except in elliptical expressions where the main verb is understood as if it were present. Auxiliary verbs always precede main verbs within a verb phrase such as in the sentence You will help me. However, in interrogative sentences,  the auxiliary appears in front of the subject  as in Will you help me? The standard for English grammar, set by The Cambridge Grammar of the English Language and other similar university  press releases, defines auxiliary verbs of English as can, may, will, shall, must, ought, need, dare as  modals  (having no infinitive form) and be, have, do, and use as non-modals (which do have infinitives).   To Be or Not to Be Helping Verbs Since some of these words are also to be verbs, which can operate as main verbs, its important to know the distinctions between the two. According to the American Heritage Guide to Contemporary Usage and Style, there are four ways in which auxiliary verbs differ from main verbs. First, auxiliary verbs do not take word endings to form participles or agree with their subject, and thus it is correct to say I may go but incorrect to say I mays go. Secondly, helping verbs come before negative clauses and dont use the word do to form them. The main verb must use do to form the negative and follows not like in the sentence We do not dance.   Helping verbs also always come before the subject in a question, whereas main verbs use do and follow the subject to form questions. Therefore, the word can in the question Can I have another apple? is an auxiliary verb while do in Do you want to go to the movies? acts as the main verb.   The final differentiation between the two forms of verbs is that auxiliary words take the infinitive without also needing the word to, like in the sentence I will call you tomorrow. On the other hand, main verbs that take an infinitive always have to use the word to, such as I promise to call you tomorrow. A Limit to Helping English grammar rules dictate that an active sentence may contain a maximum of three auxiliaries, while a passive sentence may include four, wherein the first is finite and the rest nonfinite words.   Barry J. Blake breaks down the famous Marlon Brando quote from On the Waterfront, where he says I couldve been a contender, by observing that in the example we have a modal followed by the past participle of the verb to be. Any more than three auxiliaries and the sentence becomes too convoluted to decipher. And, consequently, the helping word no longer helps clarify the main verb its meant to modify.