The Collaborative International Dictionary
Auxiliary \Aux*il"ia*ry\, n.; pl. Auxiliaries.
A helper; an assistant; a confederate in some action or enterprise.
(Mil.) pl. Foreign troops in the service of a nation at war; (rarely in sing.), a member of the allied or subsidiary force.
(Gram.) A verb which helps to form the voices, modes, and tenses of other verbs; -- called, also, an auxiliary verb; as, have, be, may, can, do, must, shall, and will, in English; [^e]tre and avoir, in French; avere and essere, in Italian; estar and haber, in Spanish.
(Math.) A quantity introduced for the purpose of simplifying or facilitating some operation, as in equations or trigonometrical formul[ae].
n. (context grammar English) A verb that accompany the main verb in a clause in order to make distinctions in tense, mood, voice or aspect.
An auxiliary verb ( abbreviated ) is a verb that adds functional or grammatical meaning to the clause in which it appears, such as to express tense, aspect, modality, voice, emphasis, etc. Auxiliary verbs usually accompany a main verb. The main verb provides the main semantic content of the clause. An example is the verb have in the sentence I have finished my dinner. Here, the main verb is finish, and the auxiliary have helps to express the perfect aspect. Some sentences contain a chain of two or more auxiliary verbs. Auxiliary verbs are also called helping verbs, helper verbs, or (verbal) auxiliaries.