So Do I / Neither Do I: Expression of Agreement

Agreeing with the previous sentence: auxiliary + subject.

Affirmative — so

• I like jazz. — So do I.
• She's tired. — So am I.
• They've finished. — So have we.
• He can swim. — So can I.

Negative — neither / nor

• I don't eat meat. — Neither do I. / Nor do I.
• She isn't ready. — Neither am I.

Order: so / neither + auxiliary + subject (inversion). This agrees about a different person. To add the same idea about the same person, use too / either: I like it too. · I don't like it either.