Paul rides a bicycle
Here, the verb rides certainly denotes an action which Paul performs - the action of riding a bicycle. However, there are many verbs which do not denote an action at all. For example, in Paul seems unhappy, we cannot say that the verb seems denotes an action. We would hardly say that Paul is performing any action when he seems unhappy. So the notion of verbs as "action" words is somewhat limited.
The Base Form
Here are some examples of verbs in sentences:
Notice that in  and , the verbs have an -s ending, while in  and , they have an -ed ending. These endings are known as INFLECTIONS, and they are added to the BASE FORM of the verb. In , for instance, the -s inflection is added to the base form travel.
Certain endings are characteristic of the base forms of verbs:
Past and Present Forms
When we refer to a verb in general terms, we usually cite its base form, as in "the verb travel", "the verb sing". We then add inflections to the base form as required.
These inflections indicate TENSE. The -s inflection indicates the PRESENT TENSE, and the -ed inflection indicates the PAST TENSE.
In sentence , She travels to work by train, we have a third person singular pronoun she, and the present tense ending -s. However, if we replace she with a plural pronoun, then the verb will change:
The verb travel in [1a] is still in the present tense, but it has changed because the pronoun in front of it has changed. This correspondence between the pronoun (or noun) and the verb is called AGREEMENT or CONCORD. Agreement applies only to verbs in the present tense. In the past tense, there is no distinction between verb forms: she travelled/they travelled.
Finite and Nonfinite Verbs
Verbs which have the past or the present form are called FINITE verbs. Verbs in any other form (infinitive, -ing, or -ed) are called NONFINITE verbs. This means that verbs with tense are finite, and verbs without tense are nonfinite. The distinction between finite and nonfinite verbs is a very important one in grammar, since it affects how verbs behave in sentences. Here are some examples of each type:
 The old lady is writing a play
Writing and produced each has another verb before it. These other verbs (is and was) are known as AUXILIARY VERBS, while writing andproduced are known as MAIN VERBS or LEXICAL VERBS. In fact, all the verbs we have looked at on the previous pages have been main verbs.
Auxiliary verbs are sometimes called HELPING VERBS. This is because they may be said to "help" the main verb which comes after them. For example, in The old lady is writing a play, the auxiliary ishelps the main verb writing by specifying that the action it denotes is still in progress.
Auxiliary Verb Types
In this section we will give a brief account of of each type of auxiliary verb in English. There are five types in total:
An important difference between auxiliary verbs and main verbs is that auxiliaries never occur alone in a sentence. For instance, we cannot remove the main verb from a sentence, leaving only the auxiliary:
Auxiliaries always occur with a main verb. On the other hand, main verbs can occur without an auxiliary.
I like my new job
In some sentences, it may appear that an auxiliary does occur alone. This is especially true in responses to questions:
Q. Can you sing?
Here the auxiliary can does not really occur without a main verb, since the main verb -- sing -- is in the question. The response is understood to mean:
Yes, I can sing
This is known as ellipsis -- the main verb has been ellipted from the response.
Auxiliaries often appear in a shortened or contracted form, especially in informal contexts. For instance, auxiliary have is often shortened to've:
I have won the lottery ~I've won the lottery
These shortened forms are called enclitic forms. Sometimes different auxiliaries have the same enclitic forms, so you should distinguish carefully between them:
I'd like a new job ( = modal auxiliary would)
He's been in there for ages ( = perfective auxiliary has)
The following exercise concentrates on three of the most important auxiliaries -- be, have, and do.
The NICE Properties of Auxiliaries
The so-called NICE properties of auxiliaries serve to distinguish them from main verbs. NICE is an acronym for:
Main verbs do not exhibit these properties. For instance, when we form a question using a main verb, we cannot invert:
[John sings] in the choir ~*[Sings John] in the choir?
Instead, we have to use the auxiliary verb do:
[John sings] in the choir ~[Does John sing] in the choir?
Among the auxiliary verbs, we distinguish a large number of multi-word verbs, which are called SEMI-AUXILIARIES. These are two-or three-word combinations, and they include the following:
Like other auxiliaries, the semi-auxiliaries occur before main verbs:
The film is about to start
I'm going to interview the Lord Mayor
I have to leave early today
You are supposed to sign both forms
I used to live in that house
Some of these combinations may, of course, occur in other contexts in which they are not semi-auxiliaries. For example:
I'm going to London
Here, the combination is not a semi-auxiliary, since it does not occur with a main verb. In this sentence, going is a main verb. Notice that it could be replaced by another main verb such as travel (I'm travelling to London). The word 'm is the contracted form of am, the progressive auxiliary, and to, as we'll see later, is a preposition.
Tense and Aspect
TENSE refers to the absolute location of an event or action in time, either the present or the past. It is marked by an inflection of the verb:
David walks to school (present tense)
Reference to other times -- the future, for instance -- can be made in a number of ways, by using the modal auxiliary will, or the semi-auxiliarybe going to:
David will walk to school tomorrow
Since the expression of future time does not involve any inflecton of the verb, we do not refer to a "future tense". Strictly speaking, there are only two tenses in English: present and past.
 David fell in love on his eighteenth birthday
In , the verb fell tells us that David fell in love in the past, and specifically on his eighteenth birthday. This is a simple past tense verb.
In  also, the action took place in the past, but it is implied that it took place quite recently. Furthermore, it is implied that is still relevant at the time of speaking -- David has fallen in love, and that's why he's behaving strangely. It is worth noting that we cannot say *David has fallen in love on his eighteenth birthday. The auxiliary has here encodes what is known as PERFECTIVE ASPECT, and the auxiliary itself is known as the PERFECTIVE AUXILIARY.
In , the action of falling in love is still in progress -- David is falling in love at the time of speaking. For this reason, we call it PROGRESSIVE ASPECT, and the auxiliary is called the PROGRESSIVE AUXILIARY.
Aspect always includes tense. In  and  above, the aspectual auxiliaries are in the present tense, but they could also be in the past tense:
David had fallen in love -- Perfective Aspect, Past Tense
The perfective auxiliary is always followed by a main verb in the -edform, while the progressive auxiliary is followed by a main verb in the -ing form. We exemplify these points in the table below:
While aspect always includes tense, tense can occur without aspect (David falls in love, David fell in love).
There are two voices in English, the active voice and the passive voice:
Passive constructions are formed using the PASSIVE AUXILIARY be, and the main verb has an -ed inflection. In active constructions, there is no passive auxiliary, though other auxiliaries may occur:
Paul is congratulating David
All of these examples are active constructions, since they contain no passive auxiliary. Notice that in the first example (Paul is congratulating David), the auxiliary is the progressive auxiliary, not the passive auxiliary. We know this because the main verb congratulatehas an -ing inflection, not an -ed inflection.
David was congratulated
We refer to this as an AGENTLESS PASSIVE