too/either... so am I / neither do I etc.

Question 1

We use too and either at the end of a sentence.

Answer 1

We use too after a POSITIVE verb:

…A: I’m happy.
…B: I’m happy too

We use either after a NEGATIVE verb:

…A: I’m not happy.
…B: I’m not happy either

Question 2

so am I = I am too

so have I = I have too (etc.)

Answer 2

…A: I’m working.
…B: So am I. (= I’m working too)

…A: I was late for work today.
…B: So was Sam.

Question 3

neither am I = I’m not either

neither can I = I can’t either (etc.)

Answer 3

…A: I haven’t got a key.
…B: Neither have I. (= I haven’t either)

…A: Kate can’t cook.
…B: Neither can Tom

Question 4

You can also use Nor (= Neither)

Answer 4

…A: I’m not married.

…B: Nor am I. or Neither am I.