1. clothes, cloth, clothing
clothes统指各种衣服，谓语动词永远是复数，
cloth指布，为不可数名词
clothing 服装的总称，指一件衣服用a piece of, an article of
2. incident, accident
incident指小事件,
accident指不幸的事故 He was killed in the accident.
3. amount, number
amount后接不可数名词，
number后接可数名词 a number of students
4. family, house, home
home 家，包括住处和家人，
house房子，住宅，
family家庭成员. My family is a happy one.
5. sound, voice, noise
sound自然界各种各样的声音，
voice人的嗓音，
noise噪音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 Lets go and see a good picture.
7. vocabulary, word
vocabulary词汇，一个人拥有的单词量，He has a large vocabulary.
word具体的单词
8. population, people
population人口，人数，China has a large population.
people具体的人
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.
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.
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. 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. 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.