need 作情态动词时用于否定句和疑问句,翻译成需要、必须,形式为：needn't do; Need...do?
作实义动词的时候可以用于肯定句、疑问句和否定句.其形式为：need(needs/needed)to do,don't(doesn't/ didn't) need to do
另外,人作主语的时候一般用不定式,比如 I need to buy a car./ I need a car.
物作主语的时候一般用 need +doing(动词ing形式),或者是need to be done.