Depending on the sense, the verb need behaves sometimes like an auxiliary verb (such as can or may) and sometimes like a main verb (such as want or try). When used as a main verb, need agrees with its subject, takes to before the verb following it, and combines with do in questions, negations, and certain other constructions: He needs to go. Does he need to go so soon? He doesn’t need to go. When used as an auxiliary verb, need does not agree with its subject, does not take to before the verb following it, and does not combine with do: He needn’t go. Need he go so soon? Unlike can and may, however, auxiliary need has no other form like could and might for the past tense: He said we need not worry about that.
