Affirmative additions to affirmative remarks are made with the structure so + auxiliary + subject.

John likes mangoes. So does Alice. (= Alice also likes mangoes.)
She must come. So must I.
He was late for the meeting. So were you.
I have finished my work. So has he.

Negative additions to negative remarks are made with the structure nor/neither + auxiliary + subject.

John didn’t come. Neither did Peter.
He doesn’t believe it. Neither do I.
I can’t solve the problem. Nor can my teacher.
Tom wasn’t there. Neither was Peter.

Negative additions to affirmative remarks are made with the structure but + subject + auxiliary + n’t/not.

He speaks German. But I don’t. (= I don’t speak German.)
I liked the film.  But Mary didn’t.
He can cook. But his wife can’t.

Affirmative additions to negative remarks are made with but + subject + auxiliary.

He doesn’t speak English. But I do. (= But I speak English.)
He can’t play cricket. But I can.
She wasn’t late. But you were.

Exercise

Make affirmative additions to the following remarks using the suggestions given in the brackets.

1. John came late. (Peter)
2. I must go now. (you)
3. Tomatoes are dear. (onions)
4. My sister lives in Paris. (her husband)
5. I have read the book. (my brother)

Answers

1. So did Peter.
2. So must you.
3. So are onions.
4. So does her husband.
5. So has my brother.

Add negative additions to the following negative remarks.

1. I don’t like fish. (my husband)
2. This book isn’t mine. (that book)
3. She doesn’t know me. (her husband)

Answers

1. Neither does my husband.
2. Neither is that book.
3. Neither does her husband.