根据动词的形式不同会产生不同的变化
He is a student. ——He is not a student（is not可缩写为isn't）
He like music.——he doesn't like music（谓语动词是实意动词，要变成主语+don't/doesn't+动词原形+其他）
He can swim——he can't swim（有情态动词，情态动词+not）
