我们须知,大部分情态动词,有两个特征:第一,没有人称和数的变化。第二,后面必须跟动词原形,抑或说省略 to的不定式(情态动词 ought除外,须跟 to do)。need 也不例外。不过,作为情态动词,need 常常用于否定句或疑问句中,间或用于肯定句。例如:(1)We needn’t go yet,for the film will be on in an hour.我们还不必去,因为电影还要一个钟头才开始。再如(2)Need you go so soon?你必须那么早就走吗? We must know that most of the modal verbs have two characteristics. First, there is no change in the number and number of people. Second, it must be followed by the original form of the verb, or the omission of to the infinitive (excluding the modal verb ought to follow to do). Need is no exception. However, as a modal verb, need is often used in negative sentences or interrogative sentences, or in affirmative sentences. For example: (1) We needn’t go yet, for the film will be on in an hour. We don’t have to go because the movie still takes an hour to start. Another example is (2) Need you go so soon? Do you have to leave early?