此处的need都是名词,need for后面接被需要的对象,如需要水need for water,而need of 前面常带个in,如著名小说Pride and Prejudice的第一句就是It is a truth universally acknowledged,that a single man in possession of a good fortune must be in want of a wife.此处的want与need 的用法相同.
其实,从这个例句中可以看出不仅有need,want可以“前加in后加of”用名词形式表达其相对应的动词的意思,还有possession,receipt等.