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.
The Base Form
Here are some examples of verbs in sentences:
 She travels to work by train
 David sings in the choir
 We walked five miles to a garage
 I cooked a meal for the family
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:
|–ate||concentrate, demonstrate, illustrate|
|–ify||clarify, dignify, magnify|
|-ise/-ize||baptize, conceptualize, realise|