POSITIVE AGREEMENT

To express positive agreement we use: SO + Auxiliary* + Subject
If there is no auxiliary in the sentence, we use DO:

- I live in London and so does Susan = I live in London & Susan lives in London.

Tom: I like pizza
Sean: So do I
= Tom likes pizza and Sean likes pizza too


* special verbs that never use DO (auxiliaries and modals): to be, have, can, could, will, would, shall, should, may, might. These verbs are repeated in the second part of this construction:

- I can speak French
- So can my sister
(= I can speak French and your sister can speak French)

- Peter will go to London for the weekend and so will his sister = Peter will go to London & his sister will go to London
- I'm going to stay here and so are you = I'm going to stay here & you are going to stay here

Colloquial We can use SUBJECT + TOO for all the sentences.

- I like pizza
- Me too

- I can speak French
- My sister too

- Peter will go to London for the weekend and his sister too
- I can speak French and you too

NEGATIVE AGREEMENT

To express negative agreement we use: NEITHER + Auxiliary + Subject
The word NEITHER can be pronounced N + I + THER or N + EE + THER. In BrE they use the first form, with a diphthong, but some people use the second form. In AmE everybody uses the second form.

NEITHER is a negative word so it is used with an affirmative verb form (we can't have a double negative in a sentence).

I don't live in Rome and neither does Susan = I don't live in Rome & Susan doesn't live in Rome.

Tom: I don't like pizza
Sean: Neither do I
= Tom doesn't like pizza and Sean doesn't like pizza

- I can't speak French
- Neither can my sister
= I can't speak French and your sister can't speak French

- Peter won't go to London for the weekend and neither will you
- I'm not going to stay here and neither are you

Colloquial Me neither    (we can only use it with the subject "Me", but not with other subjects)

- I don't like pizza
- Me neither

- I can't speak French

- Neither can my sister   (you can't say: My sister neither)