So do I / Neither do I: Agreeing in English

Me too and Me neither are natural in conversation, but English also has a more structured pattern: So do I after a positive statement and Neither do I after a negative one. Take the auxiliary from what the other person said and put it before the subject. That inversion is the key.

So + auxiliary + subject

Use so to agree with something positive. Note the word order: it looks like a question, but it isn't one.

The subject doesn't have to be I: "I was tired." — "So was Tom."

Neither + auxiliary + subject

Use neither to agree with something negative. Neither already carries the negative, so the auxiliary stays positive.

Nor works the same way and sounds a little more formal: "Neither do I" / "Nor do I." Both are correct.

Which auxiliary?

Copy whatever the other person used. If their sentence had no auxiliary — a present or past simple verb — supply do / does / did.

This is the same auxiliary logic as question tags and questions — once it's in place, all three patterns get easier together.

The casual versions, and disagreeing

In relaxed speech, Me too and Me neither do the same job without changing the auxiliary. They're natural, compact alternatives.

To disagree, flip the polarity and keep the normal word order — no inversion here.

Common mistakes

Forgetting to invert. The auxiliary comes before the subject.

"So I do" is a real phrase, but it means something else — surprised confirmation about yourself: "You've got a stain on your shirt." — "So I do!"

Double negative with neither. Keep the auxiliary positive.

Mixing the two agreement patterns. Use either the casual reply or the inverted structure, not both together.

Wrong auxiliary. Match the original: "I'm tired." — "So am I", not "So do I".

Quick exercise

Agree with each sentence using So or Neither + I.

1. "I love Italian food." — "___ ___ I."
2. "I'm not hungry." — "___ ___ I."
3. "I've been to Japan." — "___ ___ I."
4. "I can't drive." — "___ ___ I."
5. "I went to the concert." — "___ ___ I."