词性变化如下
动词long，渴望。longing名词。longing形容词。length ，名词，lengthy，adj. 漫长的，长时间的；（讲话、文章等）冗长的，过于详尽的，动词，lengthen，vt. 使延长；加长
例如
Conventional wisdom would seem to suggest that companies have no incentive to lengthen the life cycle of their products and reduce the revenue they would get from selling new goods.
