17. officer, official

　officer部队的军官，official政府官员 an army officer

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…

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

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.

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

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.

11. course, subject

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

10. road, street, path, way

　road具体的公路，马路，street街道，path小路，小径，way道路，途径

　take this road; in the street, show me the way to the museum.

9. weather, climate

　weather一天内具体的天气状况，climate长期的气候状况 The climate here is not good for you.

8. population, people

　population人口，人数，people具体的人 China has a large population.