助动词 do did doesbe,have,do,shall,will be的适当形式
情态动词can may must need dare should would will 等
系动词 be become fall get go grow feel sound seem turn appear keep remain continue stay prove 等
助动词和情态动词本身可以接not 作否定,行为动词却要根据句子所适用的助动词来变否定形式
希望能帮你