need分为行为动词和情态动词两种
行为动词:后接名词和动词不定式(to do sth),否定句要加助动词和not在前面:I don't need to telephone him.三人称单数need后加s:He needs water,过去时need加ed:He needed my help 3 years ago.
情态动词:后面直接加动词原形,否定句need后直接加not:l needn't hand in my homework.,三人称单数need后不可加s:He need hand in his homework.