12. custom, habit
custom传统风俗，习俗，也可指生活习惯，后接to do， habit生活习惯，习惯成自然，后接of doing. I've got the habit of drinking a lot. 13. cause, reason
cause 指造成某一事实或现象的直接原因，后接of sth./doing sth，reason用来解释某种现象或结果的理由，后接for sth./doing sth. the reason for being late 14. exercise, exercises, practice
exercise运动，锻炼（不可数），exercises练习（可数），practice（反复做的）练习 Practice makes perfect.
15. class, lesson
作\课\解时,两者可以替换.指课文用lesson. 指班级或全体学生用class. lesson 6; class 5
16. speech, talk, lecture
speech指在公共场所所做的经过准备的较正式的演说，talk日常生活中的一般的谈话，讲话，lecture学术性的演讲，讲课 a series of lecture on… 17. officer, official
officer部队的军官，official政府官员 an army officer 18. work, job
二者均指工作。work不可数，job可数 a good job 19. couple, pair
couple主要指人或动物，pair多指由两部分组成的东西 a pair of trousers 20. country, nation, state, land
country侧重指版图，疆域，nation指人民，国民，民族，state侧重指政府，政体，land国土，国家 The whole nation was sad at the news. 21. cook, cooker
cook厨师，cooker厨具 He is a good cook. 22. damage, damages
damage不可数名词, 损害，损失; damages复数形式, 赔偿金 $900 damages 23. police, policeman
police警察的总称，后接复数谓语动词，policeman 指某个具体的警察 The police are questioning everyone in the house. 24. problem, question
problem常和困难连系，前面的动词常为think about, solve, raise，question常和疑问连系，多和ask, answer连用 25. man, a man
man人类，a man一个男人 Man will conquer nature. 26. chick, chicken
二者均可指小鸡，chicken还可以当鸡肉 The chicken is delicious. 27. telegram, telegraph
当电报解时，telegram指具体的，telegraph指抽象的 a telegram, by telegraph 28. trip, journey, travel, voyage
travel是最常用的，trip指短期的旅途，journey指稍长的旅途，voyage指海上航行 a three-day trip
29. sport, game
sport多指户外的游戏或娱乐活动，如打球，游泳，打猎，赛马等；game指决定胜负的游戏，通常有一套规则 His favorite sport is swimming. 30. price, prize
price价格，prize奖，奖品，奖金 win the first prize The price is high/low