Auxiliary Verb

An auxiliary verb is a verb that adds functional or grammatical meaning to the clause in which it appears—for example, to express tense, aspect, modality, voice, emphasis, etc. Auxiliary verbs usually accompany a main verb.

What is an auxiliary verb?

Well, we're happy to tell you. The word "auxiliary" in general refers to a kind of supporting or helping function. An auxiliary verb is thus a supporting or helping verb. In a sentence, the auxiliary verb is not the main verb. Rather, it provides support for the main verb and modifies the sentence as a whole in some meaningful way. 

The auxiliary verb must thus be understood within the context of its relationship with the broader sentence as a whole. It is defined by the fact that it cannot meaningfully stand alone. 

Using auxiliary verbs in sentences

Here is an example of the auxiliary verb being used correctly in a sentence. 

"The man asked his coworkers what more they wanted from him, since as far as he was concerned, he had already given his all."

In this sentence, the word "had" is an auxiliary verb that modifies the main verb "given". 

Now, here is an example of the incorrect use of an auxiliary verb. 

"As a result of having drunk too much the previous evening, the man experiencing indigestion and a dull ache in his head."

The problem here is actually that the auxiliary verb is missing: the sentence should say "the man was experiencing". 

For your reference, here are a couple rules you can follow in order to make sure you are using the auxiliary verb in a correct way. 

1. The auxiliary verb always has a relationship with some other verb within a sentence (thus creating a verb phrase). Indeed, that is why it is called an auxiliary verb. Its function is dependent on its relations with other parts of grammar; it cannot indicate anything in and of itself. 

2. In general, the most important thing to keep in mind when using an auxiliary verb is to make sure that you are using the right one within the context to convey the meaning you want to convey. This often depends on tense. For example, you could say that you "are going" somewhere, or that you "had gone" somewhere. 

Function compared to other verbs

The auxiliary verb doesn't serve the same function as the regular verb. This is because whereas a regular verb usually expresses an action of some kind, the auxiliary verb only modifies another verb that is expressing an action. It is thus mainly called a verb not because of its actual function, but rather because the words that serve the purpose can often also be used as a main verb. Good examples of this are the auxiliary verb function served by the regular verbs "is" and "have". 

In a way, you could think of the auxiliary verb as a verb that primarily performs the "action" of changing the tense or aspect of a sentence. The auxiliary verb is needed in order to make modifications to a sentence that express the relationship between action and time or mood. However, the auxiliary verb as such cannot express anything by itself. It merely changes what is being expressed by something else. Again, this is the very meaning of the term auxiliary in the first place: the auxiliary verb fulfills a supporting and/or helping function. You probably use the auxiliary verb all the time, without even realizing that you are doing so.