The verb must agree with the subject in number and person, i.e., it must be of the same number (singular / plural) and person as the subject.
- He likes singing.
- They like singing.
Here the subjects he and they are in the same person – third – but the first is singular and the second is plural in number. The verb like has two forms in the third person - likes and like. The form likes is used with singular nouns, while the form like is used with plural nouns.
Thus we find that the verb must agree with its subject in number and person. That is it must be of the same number and person as its subject.
Nouns usually have -s ending in the plural. Verbs have no -s ending in the plural.
- The bird flies. / The birds fly.
- The boy sings. / The boys sing.
- The star shines. / The stars shine.
You will have noticed that only the third person singular has different endings. The verb remains unchanged in all other forms.
The verb be (is, am, are, was and were) has different forms in the singular, but not in the plural.
First person singular: I am / I was
First person plural: We are / we were
Second person singular: You are / you were
Second person plural: You are / you were
Third person singular: He is / she is / it is / he was / she was / it was
Third person plural: They are / they were