common: implies usual everyday quality or frequency of occurrence: a ~ error; lacked ~ honesty; and may additionally suggest inferiority or coarseness: his ~ manners shocked her family.  又如a common bird/name/disease/mistake/practice/people/courtesy常见鸟/常用名/常见病/常犯的错误/惯例/百姓/一般的礼貌           (coarse粗糙implies roughness, rudeness, crudeness, or insensitiveness of spirit, behavior, or language指言语行为精神等粗糙粗鲁原始不敏感，如found the coarse humor of her coworkers offensive同事粗糙的幽默感冒犯了她，如coarse wine糙酒，本例common manner等于coarse manner粗糙的举止)


ordinary: stresses accordance in quality or kind with regular order of things: an ~ pleasant summer day; a very ~ sort of man.    （regular常规例行通常stresses conformity to a rule, standard, or pattern表示符合规则标准模式，如the regular monthly meeting of the organization例会, 如本例regular order通常的"等级" ，如regular cup/bus/coffee/普杯/班车/含咖啡因的咖啡）   (order这里表示等级a level of quality，如a product of highest order顶级品，如the job requires diplomatic skills of a high order这项工作要求高超的外交技巧，如order of magnitude数量级，表示10的整数倍，如1个数量级是10倍，2个数量级two orders of magnitude是100倍，3个是1000倍，以上order都表示级别)


plain: suggests ordinariness and homely simplicity: she comes from ~, hard-working stock.    homely简单舒适不奢华不浮夸，形容人相貌指"其貌不扬"     （又如便衣plain cloth易懂的语言plain English；plain平凡除了表示普通ordinary还表示homely不装饰不浮夸朴素和simplicity简单朴素，《平凡的世界》译名是ordinary world，但用plain似乎更好，上一个词ordinary是符合通常等级常规常识，即普通平常，如ordinary day/man普通平常的一天/平常的人，但感觉作者不是强调符合通常等级常规常识，而是强调不加粉饰无以浮夸homely simplicity的意思，比ordinary多了些褒义）    


familiar: stresses the fact of being generally known and easily recognized: a ~ melody.   如谚语familiarity breeds contempt熟悉生轻蔑，太熟悉的东西会被轻视


popular: applies to what is accepted by or prevalent among people in general sometimes in contrast to upper classes or special groups: a hero typically found in ~ fiction.    popular music/culture/fiction流行(通俗)音乐/文化/小说，如popular vote是选民投票，对应于electoral college vote选举学院投票


vulgar: otherwise similar to popular, is likely to carry derogatory connotations of inferiority or coarseness: goods designed to appeal to the ~ taste.     如three vulgarities三俗，如"but if life is not a vulgar flare amid the cool radiance of the stars, ......if beauty means something如果生命不是冷冷星辉中的卑俗闪烁，......如果美有某种意义"


common常用常见: 指每日通常频繁发生，也可指劣质粗糙，ordinary普通: 强调符合通常等级(regular order of things)，如性质种类，plain普通朴素平凡: 表示普通并且简朴，familiar熟悉: 指广为人知容易辨识，popular大众流行: 指被大众接受和流行，相对上层特殊阶层，vulgar粗俗: 常带有劣质粗糙的贬义


记忆方法: 1）首字母COPFPV重组成PVC聚氯乙烯和FOP纨绔子弟<==普通         "普"的意思是"数量全、范围广"，从日并声，字面上是"二人并排站着，太阳在下方"，说文: "普，日无色也"，"日无光，则近远皆同"，因而表示数量全范围广，如普遍普通普快普世普天普查普选普及普法

        2）普通的意思是常遇见不特别mean generally met with and not in any way special, strange, or uncommon.   general两个意思  1、普遍通用，涉及属于关于全部或几乎全部，所以通用，如general election普选大选，general purpose通用  2、大致总体，而不精确，如语言、想法等，如general idea大意general description概述总体描述