To do can be used as an auxiliary verb or a main verb that has its own meaning. As a main verb it also forms the continuous form doing. [TO BE CHECKED WITH A LINGUIST.] To do is an irregular verb and in the affirmative, negative and interrogative form in present and past tenses it has these kinds of structures and forms:
To Do Affirmative
Subject + to do + …
|Subject||To Do in Present Simple||To Do in Past Simple|
To Do Negative
Subject + to do + not + …
|Subject||To Do in Present Simple + not||Short Form*||To Do in Present Simple + not||Short Form*|
|I||do not||don’t||did not||didn’t|
*The short form is used in spoken language or in informal writing.
To Do Interrogative
To do + subject + …?
|To Do in Present Simple||To Do in Past Simple||Subject||Question Mark|
We use the verb to do as:
- An auxiliary verb: to form negatives and interrogative of other verbs, as well as for emphasis and negative imperatives;
- A main verb: in the meaning of to perform or to complete an action.
External link to Ресми: To Do exercises (10).