So, neither and either short responses

“I love hiking.” “So do I.” You agree without repeating the whole sentence.

Agree with a positive statement

Use So + auxiliary + subject:

• I’m tired. → So am I.
• I like jazz. → So do I.
• I went yesterday. → So did we.
• She can swim. → So can her brother.

Choose the auxiliary that matches the first sentence. If there is no auxiliary, use do/does/did.

Agree with a negative statement

Use Neither + auxiliary + subject, or a negative clause with either at the end:

• I don’t like olives. → Neither do I. / I don’t either.
• He isn’t ready. → Neither am I. / I’m not either.
• She can’t drive. → Neither can I. / I can’t either.

With neither, the auxiliary itself is positive: Neither do I, not Neither don’t I. Either follows a negative clause.

Choose the helper from the sentence you are responding to

The new subject can change the helper: I like tea. So does my sister. The first statement has I, but the reply refers to my sister, so does is needed.

For negative agreement, use the same logic with neither: I haven't finished. Neither has Ben. Ben takes has.

Compare the two orders

So do I means the same positive statement applies to me too. I do too expresses that agreement with ordinary subject-helper order.

Neither do I means the negative statement applies to me too. I don't either uses ordinary order and puts either at the end.

The word order is part of the construction: so/neither + helper + subject. Avoid So I do when you intend simple agreement about another person's statement applying to you.

A short conversation

A: I’ve never visited Scotland.
B: Neither have I. But my sister has.

The response Neither have I picks up the present perfect in I’ve never visited. The next sentence adds new information.

Compare with simpler replies

Me too is a common informal response to a positive statement. Me neither is common informally after a negative one. So do I and Neither do I let you show the tense and subject clearly, which is useful in more careful speech and writing.

Agreeing with a negative is still agreement

If your friend says I don't like horror films, Neither do I means you share that dislike. You are not disagreeing with your friend.

To disagree, use a short positive clause:

A: I don't like horror films.
B: I do. I like the suspense.

For a positive statement, disagree with a negative response: I love running. I don't; I prefer cycling. So and neither are for matching the first statement, not for every kind of reply.

Never makes the first statement negative

I've never tried skiing invites Neither have I. Never supplies the negative meaning, even without not.

With either, keep a negative clause: I haven't tried it either. Do not use I haven't tried it too for this standard negative-agreement meaning.

Me too and me neither are common informal replies. So do I and Neither do I are particularly useful when you want the tense or another subject to be explicit.

Consider a longer exchange:

A: I'm tired, but I haven't finished the exercise.
B: So am I. And I haven't finished either.
A: Jo has finished.
B: So has Sam. We could ask them for help.

The first reply agrees about tiredness with am. The next agrees about an unfinished exercise with haven't. The last adds another person to a positive present-perfect statement with has.

To respond accurately, identify the exact idea you are agreeing with. A sentence may contain both positive and negative information. Choosing a helper without checking the meaning can create a reply that says something you did not intend.

Sources and further reading

• Cambridge Dictionary: So am I, so do I, neither do I