Learn English – How to agree with a negative statement: with “yes” or with “no”

A sentence becomes negative by specific words. Most of those have 'no' in it. For example

No
Nobody
No one
Never
Not
Nowhere
...

And yes a sentence without a subject can be negative. Here's an example:

Stop the car!  -- positive
Do not stop the car! -- negative

Do your homework!
Don't do drugs! 

There are only a few markers in English which make a question a "negative-polarity" question:

• No
• Not
• Nothing
• Never

And any of their combined/contracted forms ("cannot", "don't", wasn't", etc.)

If and only if any of these appear in the sentence, it is considered a negative-polarity sentence and the "agreeing" response uses "neither":

• I had no idea.
• I was not present at the time.
• I had nothing to do with it.
• I never heard any complaints.

agreeing reply = Me neither!

A prefix on a word which reverses its meaning, even "non-", does not convert the sentence to negative polarity:

He was very non-committal.
- So was she.