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.

31. a number of, the number of

a number of许多，谓语动词用复数。the number of…的数目，谓语动词用单数。The number of students is increasing.

32. in front of, in the front of

in front of范围外的前面，in the front of范围内的前面 In the front of the room sits a boy.

33. of the day, of a day

of the day每一天的，当时的，当代的， of a day暂时的，不长久的 a famous scientist of the day

34. three of us, the three of us

three of us我们(不止三个)中的三个，the three of us我们三个(就三个人)The three of us---Tom, Jack and I went to the cinema.

35. by bus, on the bus

by bus表手段，方式，不用冠词，on the bus表范围 They went there by bus.

36. for a moment, for the moment

for a moment 片刻，一会儿，for the moment暂时，一时 Thinking for a moment, he aGREed.

37. next year, the next year

next year将来时间状语，the next year过去将来时间状语 He said he would go abroad the next year.

38. more than a year, more than one year