5. sound, voice, noise
sound自然界各种各样的声音;
voice人的嗓音;
noise噪音 eg:I hate the loud noise outside.
6. photo, picture, drawing
photo用照相机拍摄的照片;
picture可指相片，图片，电影片;
drawing画的画 eg:Lets go and see a good picture.
7. vocabulary, word
vocabulary词汇，一个人拥有的单词量;
word具体的单词 eg:He has a large vocabulary.
8. population, people
population人口，人数;
people具体的人 eg:China has a large population.
9. weather, climate
weather一天内具体的天气状况;
climate长期的气候状况 eg:The climate here is not good for you.
10. road, street, path, way
road具体的公路，马路;eg:take this road
street街道;eg:in the street
path小路，小径;
way道路，途径 eg:show me the way to the museum.
11. course, subject
course课程(可包括多门科目);eg:a summer course
subject科目(具体的学科)
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. eg:Ive 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. eg: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 eg: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. eg: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 eg:a series of lecture on