Look at these sentences;
I go to the school to study.
He goes to the school to study.
In first sentence, the verb go has I for its subject and it agrees with it. In second sentence, since the subject is he, we have used the verb goes. In these sentences, the verb is limited by the person of the subject.
Now look at these two sentences;
He goes to the school to study. (Singular subject singular verb)
They go to the school to study. (Plural subject plural verb)
A verb that is limited by the person and number of the subject is called a finite verb.
But the sentences given above have another verb also; to study. This verb does not have a subject. It simply names the action denoted by the verb study. Its form does not change. (In all the sentences above, it has the sane form; to study).
A verb not limited by person and number is called a non-finite verb.
There are three groups of non- finites;
The infinitive : It is also referred to as the to-verb . but it can be used with or without to also.
For example: to steal, to forget, to write (present infinitive)
to have stolen ,to have forgotten (perfect infinitive)
The participle : A word which is like a verb but performs the work of an adjective is called participle. There are two kinds of participle present participle and past participle.
For example: stealing, forgetting, writing (present participle)
Stolen, forgotten, written (past participle)
The gerund : A word which is like a verb but performs the work of a noun is called a gerund.
For example: stealing, forgetting, writing
The present participle and the gerund have the same from- what we normally describe as the – ing form. But their functions are quite different. The participle is partly a verb and an adjective, the gerund is partly a verb and partly a noun.
I want to play. (to infinitive)
She can play chess very well. (play is an infinitive without to)
The broken window had to be replaced (broken is behave like a participle)
I am tired of your grumbling. (grumbling is a gerund)