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.