Short Answers

Saying Yes, I do. / No, I dont in English is more polite than just saying Yes. / No. Thats why short answers are very commonly used.

To form the short answer, you use the first word from the question. (This is either an auxiliary verb or a form of be.)

Use the long form (he does) in affirmative answers (yes).

Use the short form (he doesnt) in negative answers (no).

Do we know him? Yes, we do. No, we dont.
Can she see me?Yes, she can.No, she cant.
Have they read the book?Yes, they have.No, they havent.
Is he hungry?Yes, he is.No, he isnt.

Mind: If you is the subject of the question, you must be replaced by I or we.

Do you know him? Yes, I / we do. No, I / we dont.

If the question starts with are you, are must sometimes be replaced by am.

Are you hungry? Yes, I am. No, Im not.
But: → Yes, we are. No, we arent.

Exercises on Short Answers