Verbs have traditionally been defined as "action" words or "doing" words. The verb in the following sentence is rides: 

            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. 

We can achieve a more robust definition of verbs by looking first at their formal features. 

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Here are some examples of verbs in sentences: 

            [1] She travels to work by train

            [2] David sings in the choir

            [3] We walked five miles to a garage

            [4] I cooked a meal for the family 

Notice that in [1] and [2], the verbs have an -s ending, while in [3] and [4], they have an -ed ending. These endings are known as INFLECTIONS, and they are added to the BASE FORM of the verb. In [1], for instance, the -s inflection is added to the base form travel. 

Certain endings are characteristic of the base forms of verbs:

Ending	Base Form
-ate	concentrate, demonstrate, illustrate
-ify	clarify, dignify, magnify
ise/-ize	baptize, conceptualize, realise

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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. 

	Base Form	+	Inflection
[1] She	travel	+	s	to work by train
[2] David	sing	+	s	in the choir
[3] We	walk	+	ed	five miles to a garage
[4] I	cook	+	ed	a meal for the whole family

These inflections indicate TENSE. The -s inflection indicates the PRESENT TENSE, and the -ed inflection indicates the PAST TENSE. 

Verb endings also indicate PERSON. Recall that when we looked at nouns and pronouns, we saw that there are three persons, each with a singular and a plural form. These are shown in the table below.

Person	Singular	Plural
1st Person	/	we
2and person	you	you
3rd person	he/she/John/the dog	they/the dogs

In sentence [1], 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: 

            [1] She travels to work by train

            [1a] They travel to work by train 

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.  

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