1. a number of，the number of

a number of 许多，谓语动词用复数；
the number of …的数目，谓语动词用单数。
The number of students is increasing.学生的数量在增长。

2. in front of，in the front of

in front of 范围外的前面；
in the front of 范围内的前面。
In the front of the room sits a boy.
在这个房间前面坐着一个男孩。

3. three of us，the three of us

three of us 我们（不止三个）中的三个；
the three of us 我们三个（就三个人）。
The three of us——Tom, Jack and I went to the cinema yesterday.
我们三个——汤姆、杰克和我昨天去看电影了。

4. by bus, on the bus

by bus 乘公交车，表手段，方式，不用冠词；
on the bus 在公交车上，表范围。
They went there by bus last year.
去年，它们乘公交车去的那里。

5. for a moment, for the moment

for a moment 片刻，一会儿；
for the moment 暂时，一时。
Thinking for a moment, he agreed.
想了一会儿，他同意了。

6. next year, the next year

next year 明年，将来时间状语；
the next year 第二年，过去将来时间状语。
He said he would go abroad the next year.他说他第二年会出国。

7. take advice, take the(one's) advice

take advice 征求建议；
take the advice 接受建议。
He refused to take the advice and failed again.他拒绝接受建议，再一次失败了。

8. in a word；in words

in a word 总之，一句话；
in words 口头上。
In a word, you are right.
总之，你是对的。

9. in place of, in the place of

in place of 代替；
in the place of 在…...地方。
A new building is being built in the place of the old one.
一座新的建筑物在原来旧的建筑物所在地正在被建。

10. in secret, in the secret

in secret 秘密地，暗自地，偷偷地，一般用作状语；
in the secret 知道内情，知道秘密，一般用作表语。
My mother was in the secret from the beginning.
我妈妈从一开始就知道内情。

11. go to sea, by sea, by the sea

go to sea 当海员，出航；
by sea 乘船，由海路；
by the sea 在海边。

12. the doctor and teacher, the doctor and the teacher

the doctor and teacher 指一个人，既是医生又是老师；
the doctor and the teacher 两个人，一个医生和一个老师。

13. in charge of, in the charge of

in charge of 负责，掌管；
in the charge of 被负责，被掌管。
He is in charge of the matter.
他负责这件事。
The matter is in the charge of her.
这件事被她负责。

14. in class, in the class

in class 在课上；
in the class 在班级里。
He is the best student in the class.
他是班里最好的学生。

15. on fire, on the fire

on fire 着火；
on the fire 在火上。
Put the food on the fire.
把食物放在火上。
The house is on fire.
房子着火了。

16. out of question, out of the question

out of question 毫无疑问的；
out of the question 不可能的。

17. by day；by the day

by day 白天；
by the day 按天计算。
The workers are paid by the day.
工人们按天被支付工资。

18. the people, a people

the people 指民，人们；
a people 指民族。

19. no more than；not more than

no more than 相当于only，仅仅，只有；
not more than 至多，不超过。

20. by oneself；for oneself；

to oneself；of oneself
by oneself 单独，独自；
for oneself 亲自；
to oneself 供自己用；
of oneself 自动。
The door opened of itself.
这扇门自动开了。

21. at all；after all

at all 根本，全然；
after all 到底，毕竟。
After all he is a child.
他毕竟是个孩子。

22. at ease；with ease

at ease 舒适地，安逸地；
with ease 容易地，无困难地。

23. day after day；day by day

day after day 日复一日地（无变化）；
day by day一天天地（有变化）。
Trees grow taller day by day.
树木一天天地长高了。

24. on the corner, in the corner, at the corner

on the corner 物体表面的角上；
in the corner 物体内部的角落里；
at the corner 物体外部的角落上（拐角处）。

25. warn sb. of；warn sb. against

warn sb. of 提醒某人注意某事；
warn sb. against提醒某人不要做某事。

26. at peace；in peace

at peace 平静地；
in peace 和平地。

27. on earth, on the earth, in the earth

on earth 在世上，在人间，到底，究竟；
on the earth 在地上，在地球上；
in the earth 在地下，在泥土里。

28. in surprise, to one's surprise

in surprise 惊奇地；
to one's surprise 令某人吃惊的是。

29. in the air, on the air, in the sky

in the air 正在酝酿中；
on the air 播送，广播；
in the sky 在天空中。
His show is on the air at 6:00 tonight.
他的节目今晚六点播送。

30. in the field, on the field

in the field 在野外；
on the field 在战场上。
He lost his life on the field.
他在战场上失去了生命。

31. in the market, on the market

in the market 在市场上，表示场所或地点；
on the market 在出售。
He sells fish in the market.
他在市场卖鱼。
Fresh vegetables are on the market now.
新鲜的蔬菜现在正在出售。

32. in the sun, under the sun

in the sun 在阳光下；
under the sun 地球上，全世界。

33. in a voice, with one voice

in a voice 出声地；
with one voice 异口同声地。
They refused with one voice.
他们异口同声地拒绝。

34. All right. That's all right. That's right.

All right. That's all right. 当好吧解时，可以替换；当不客气，没关系解时只能用“That's all right. ”
That's right. 那是对的 。