只要有否定词就是否定句吗?如题……那根据什么来判断一个句子是否是否定句呢？

I had hadrly done my homework.
hardly 几乎不
但 这是一个肯定句
所以
有 否定词未必是 否定句。
I don't know.

不一定,如Don't you know that?；I can't imagine that he won't come.

不一定.有了否定词,只能说明句子是否定意思,但未必是否定句.