11. course, subject

course课程(可包括多门科目),subject科目(具体的学科)a summer course.

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.