the exact opposite of something, or a complete lack of it

She sees faith as a negation of reason. 她认为信仰是对理性的否定。

the act of saying no

She shook her head in negation. 她摇头表示拒绝。

the act of saying that a sentence or part of a sentence is not true, or an instance of this

Negative declaratives are clauses in which sentential negation is expressed by "not". 否定陈述句是用“不”表示否定的句子。