Negative and Interrogative use of Present Indefinite in English Grammar

Affirmative Formation of Present Indefinite Tense:

There are two sets of subjects i.e.

1) 1st person, 2nd person and all plurals which take 1st form of verb.

I go to school.

We like parties.

2) 3rd person singular/ single nouns take 1st form of verb with the addition of s, es etc.

He goes to school.

Man prefers honor.

Interrogative and Negative Formation of Present Indefinite Tense:

Do is used as a helping verb to form negative or interrogative sentences; however, it is quite interesting that do is also a verb which may take different forms. We also know that form of verb cannot be changed twice in a single clause, therefore; we may change form of the verb which comes first in a given clause.

1) He does not go to school. ( Change in verb form)

2) Teachers do not fulfill their commitment. (Change in verb form i.e. first form of verb is used with the verb which comes first and not the verb fulfill which comes latter to that.

The same rule is applied to interrogative sentences of this tense:

Does he go to school?

Do teachers fulfill their commitment?