Dictionary.com
Thesaurus.com

auxiliary verb

American  
[awg-zil-yuh-ree vurb, -zil-uh-] / ɔgˈzɪl yə ri ˌvɜrb, -ˈzɪl ə- /

noun

Grammar.
  1. a verb used before and together with certain forms of other verbs, such as infinitives or participles, to express distinctions of tense, duration, possibility, obligation, etc., as in I am listening, We have spoken, They can see, Did you go?


auxiliary verb British  

noun

  1. a verb used to indicate the tense, voice, mood, etc, of another verb where this is not indicated by inflection, such as English will in he will go, was in he was eating and he was eaten, do in I do like you, etc

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

auxiliary verb Cultural  
  1. A “helping” verb that modifies the main verb, as in “Gail can win,” “Gail did win,” “Gail could have won.” A question often begins with an auxiliary verb: “Did Gail win?” “Could Gail lose?” The various forms of the verbs can, have, is, and does frequently act as auxiliaries.


Etymology

Origin of auxiliary verb

First recorded in 1755–65

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Similarly, the allegedly unsplittable verb will execute is not a verb at all but two verbs, the auxiliary verb will and the main verb execute.

From "The Sense of Style" by Steven Pinker

The active participles, preceded by the auxiliary verb esti = to be, in its various moods and tenses, form the compound tenses of the active voice.

From The International Auxiliary Language Esperanto Grammar and Commentary by Cox, George

“Where can they be?” asked the master, with a strong accent on the auxiliary verb.

From Humorous Ghost Stories by Scarborough, Dorothy

Keeping to the auxiliary verb to be, we find that I am is in Sanskrit Greek Lithuanian asmi esmi esmi.

From Lectures on The Science of Language by Müller, Max

As incorporated in the verbal form as an auxiliary verb.

From The Philosophic Grammar of American Languages, as Set Forth by Wilhelm von Humboldt With the Translation of an Unpublished Memoir by Him on the American Verb by Brinton, Daniel Garrison