1. clothes, cloth, clothing
clothes統指各種衣服，謂語動詞永遠是復數，
cloth指布，為不可數名詞
clothing 服裝的總稱，指壹件衣服用
a piece of, an article of
2. amount, number
amount後接不可數名詞，
number後接可數名詞?
a number of students
3. sound, voice, noise
sound自然界各種各樣的聲音，
voice人的嗓音，
noise噪音
I hate the loud noise outside.
4. cause, reason
cause 指造成某壹事實或現象的直接原因，
後接of sth./doing sth，
reason用來解釋某種現象或結果的理由，
後接for sth./doing sth. the reason for being late
5. exercise, exercises, practice
exercise運動，鍛煉（不可數），
exercises練習（可數），
practice（反復做的）練習
Practice makes perfect.
6. officer, official
officer部隊的軍官，
official政府官員
an army officer
7. work, job
二者均指工作。
work不可數，job可數 a good job
8. cook, cooker
cook廚師，cooker廚具
He is a good cook.
9. problem, question
problem常和困難聯系，
前面的動詞常為think about, solve, raise，
question常和疑問聯系
多和ask, answer連用
10. a number of, the number of
a number of許多，謂語動詞用復數。
the number of…的數目，謂語動詞用單數。
The number of students is increasing.
11. chick, chicken
二者均可指小雞，
chicken還可以當雞肉
The chicken is delicious.
12. trip, journey, travel, voyage
travel是最常用的，
trip指短期的旅途，
journey指稍長的旅途，
voyage指海上航行
a three-day trip
13. in front of, in the front of
in front of範圍外的前面
in the front of範圍內的前面
In the front of the room sits a boy.
14. three of us, the three of us
three of us我們（不止三個）中的三個，
the three of us我們三個（就三個人）
The three of us---Tom, Jack and I went to the cinema.
15. by bus, on the bus
by bus表手段，方式，不用冠詞，
on the bus表範圍
They went there by bus.
16. for a moment, for the moment
for a moment 片刻，壹會兒，
for the moment暫時，壹時
Thinking for a moment, he agreed.
17. in a word, in words
in a word總之，壹句話，
in words口頭上
In a word, you are right.
18. in place of, in the place of
in place of代替，
in the place of在…地方
A new building is built in the place of the old one.
19. go to sea, by sea, by the sea
go to sea當海員，出航，
by sea乘船，由海路，
by the sea在海邊 go by sea
20. the doctor and teacher, the doctor and the teacher
the doctor and teacher
指壹個人，既是醫生又是老師，
the doctor and the teacher
兩個人，壹個醫生和壹個老師