difficulty: can apply to any condition, situation, experience, or task which presents a problem hard to solve or seemingly beyond one's ability to suffer or surmount: they were determined to succeed, they met and solved each ~ as it arose.       problem问题applies to any question or difficulty calling for a solution or causing concern泛指需要关注解决的问题困难，如the problems created by high technology高技术带来的问题，可见problem和difficulty互释


hardship: stresses extreme suffering, toil, or privation but does not necessarily imply either effort to overcome or patience in enduring: faced many ~s that long, hard winter.   privation贫困implies a lack of the basic things that people need for living缺乏基本生活资料如衣物粮食，如they endured five years of privation during the second world war二战忍受了5年贫困生活  suffer表示遭受折磨煎熬，和后两个词意思接近


rigor: suggests a hardship necessarily imposed upon one by, for example, an austere religion, a trying climate, or an exacting undertaking: endured the ~s of a rite of initiation.        necessarily不可避免的，必然cannot be avoided，如the number of places available is necessarily limited名额必然(不可避免地)有限，如the most desirable properties necessarily command astonishingly high prices最值得拥有的财产必然要价不菲              austere苦行的allowing no pleasure or comfort，如宗教、风格     trying困难的difficult，如trying times/climate困难时刻/恶劣天气   exacting要求高的demanding hard work and care，如exacting work/man/undertaking艰巨的工作/要求严格的/艰巨事业


vicissitude: applies to an inevitable difficulty or hardship that occurs in connection with life or a way of life, a career, or a course of action: the ~s of life left them tired, bitter, and alone.  vicissitude强调change变故，但原文没有体现        俞老师好像喜欢这个词，在红包书里有这个例句the vicissitudes of life人生的枯荣沉浮，也挺喜欢          


difficulty困难: 泛指任何难以克服的问题，hardship艰难辛苦: 强调遭受劳苦、贫困，rigor严苛严酷: 指必然（不可避免）的艰难，如因宗教气候事业 ，vicissitude变迁沉浮兴衰枯荣: 指生命中难免的变故等困难，


记忆方法: 1）首字母DHRV，把V反过来，就成了HARD<==艰难      "艰"从堇艮声，本义是灾难，引申为困难。"堇"是旱灾，"艮"是转身: 面对严重旱灾人们只有转身离去，即本义灾难(土地难耕)，引申为极大的困难，如如艰难艰辛艰困举步维艰艰深晦涩     "难"本义也是灾难，由堇隹组成，堇表示灾难，"隹"表示和鸟有关，和堇艮简化成艰一样，堇隹简化成难，引申为不容易、困难。   "辛"是"身心劳苦"，起源有多种说法，有说刑具，有说树枝做成的代表奴隶身份的帽子，有说押运犯人的工具，都表示"身心劳苦"，后也指味道刺激

         2）艰难的意思是严重阻碍mean something obstructing one's course and demanding effort and endurance if one's end is to be attained.