Auxiliary Verbs
The place of auxiliary verbs is usually before the main verb in a positive sentence. We use auxiliary verbs to make negative sentences and questions.
Negative Sentences
To make a negative sentence, we usually put "not" after the auxiliary verb.
Examples:
She is not / isn't my classmate.
They do not / don't live in London.
You should not / shouldn't smoke here.
Questions
To make a question, we usually put the auxiliary verb before the subject.
Examples:
Were you at home last night?
Does he have a car?
Can I open the window?
"Do" and "does" are only used in negative sentences and questions. We don't usually use them in positive sentences.
The verbs "am", "is", "are" (Present Simple), and "was", "were" (Past Simple) can act as both the main verb and the auxiliary verb.
Some auxiliary verbs like "can", "may", "should" etc. add extra meaning to the sentence.
Examples:
It may rain tonight. (possibility)
I can play the piano well. (Ability)
You shouldn’t eat a lot at night. (Advice)
RELATED TOPIC
Exercises
Complete the sentences with the correct auxiliary verb: am, is, are, was, were, do, does, can, should, may.
1____ you at school yesterday?
Were you at school yesterday?
2She ____ speak German well. (not able)
She can't / cannot speak German well.
3____ they like football?
Do they like football?
4I ____ not feel well today.
I don't / do not feel well today.
5We ____ go to the park tomorrow. (possibility)
We may go to the park tomorrow.
6____ he have a pet?
Does he have a pet?
7You ____ eat more vegetables. (advice)
You should eat more vegetables.
8They ____ at home now.
They are / aren't / are not at home now.
9I ____ sorry for being late.
I am sorry for being late.
10You ____ use your phone in class. (not allowed)
You can't / cannot use your phone in class.