否定句的变化需根据不同的句式考虑,通常有以下几点：
1.陈述句的否定形式通常使用特殊动词（助动词和情态动词）带否定词not表示,变化方式为：找出句中的
特殊动词,在其后加not;如句中无特殊动词,则根据谓语动词形式,在谓语动词前加don't（原谓语动词为原型）,doesn't（原谓语动词为-s形式）或didn't（原谓语动词为过去式）,谓语动词都用原型.
如：He can speak English.---- He can't(can not) speak English.
She went to the movie last night.---- She didn't go to the movie last night.
2.祈使句的否定形式通常在其句首加Don't.
如：Sit over there.---- Don't sit over there.注：let's引导的祈使句的否定形式在let's后加not
