Use and form of “So/Neither do I” and “I think so”

So and neither

Jack: I’m hungry.
Jill: So am I. I haven’t eaten anything all day.
Susan: Neither have I. I didn’t have time for breakfast.

We use so after a positive statement and neither after a negative one.
• I’m hungry. –So am I.  (= And I am hungry. / I am hungry, too.)
• I haven’t eaten. –Neither have I.  (=And I haven’t eaten. / I haven’t eaten either.)

The form is so/neither + an auxiliary + subject.
The auxiliary is a form of be or have or a modal verb, eg. can.
• We’re really busy at school. –So are we.
• Judy has gone to the cinema. –So has Jane.
• Jill can’t play the piano, and neither can I.

The subject comes at the end.
• We’re busy. –So are we.   NOT   So we are.

In the Present Simple and Past Simple we use a form of do.
• Sam likes old movies. –So do I.
• Arsenal won, and so did Manchester United.
• My cellphone doesn’t work. –Neither does mine.

We can use nor instead of neither.
• I’m not there yet. Neither/nor is John.

 

I think so, etc.

Vicky: It’s “EastEnders” at eight, my favourite soap opera.
Are we going to be back in time?
Daniel: I think so.
Rachel: We might miss the beginning.
Vicky: Oh, I hope not. I want to see if Bianca will tell Tiffany the truth.

Here “I think so means “I think we’ll be back in time”, and “I hope not means “I hope we don’t miss the beginning”.

We can use so after be afraidbelieveexpectguesshopesuppose, and think.
• Do you think you’ll get the job? -Well, I hope so.
• Are you going on holiday this year? -Yes, I expect so.
• I don’t know for sure if Henry is rich, but I should think so.

But we cannot use so after know or be sure.
• There’s been an accident. -Yes, I know.  NOT  I know so.
• Are you sure you’re doing the right thing? -Yes, I’m sure.  NOT  I’m sure so.

 

There are two negative structures.

NEGATIVE + so POSITIVE + NOT
  • Is it snowing?
-I don’t think so.
• Are you going to the concert?
-I don’t expect so.
  • Is it snowing?
-I hope not.
• Have you won a prize?
-I’m afraid not.
With expect and think we normally use the negative and so. With be afraid, guess and hope we use the positive and not.

We can use believe and suppose in either structure.
• Will there be any seats left?
-I don’t suppose so.  OR   -I suppose not.