(1) A back number（过期书刊，过时的人）：
(i) Mr Lim has left the cabinet and is now a back number.
(ii) Sometimes, a back number costs more than a current number.

(2) Look after number one（照顾私利）：
Max is very selfish, often looking after number one.

(3) One’s number two（坐第二把交椅的人）：
When David could not attend a meeting, he sent his number two to deputise for him.

(4) At one time（从前有个时期）:
At one time, a few of us often had lunch together.

(5) Back to square one（打回原形）：
Mr Su is not successful in business, so he is almost back to square one.

(6) At one with... （和……看法一样）：Henry and Christine have never been at one with each other, no matter what the subject of discussion is.

(7) One up on... （比……有利）：
As your child has a better head start, he is one up on his peers.

(8) It’s all one to...（对……都没什么差别）：
To the seaside or to the park? It is all one to me as long as we go out today.

(9) One of these days（最近）：
If Harry goes on littering, he will get into trouble one of these days.

(10) In two minds about（对……三心两意）：
Irene is still in two minds about going to her former boy friend’s wedding party.

(11) It cuts both ways（有利也有弊）：
Jim asked Mary not to go to the party. But it cuts both ways. Mary now expects Jim to stay at home with her.

(12) Put two and two together（根据事实推断）：
Since Susan is neither at home nor at work, Bob puts two and two together and guesses that she should be in the shopping centre.

(13) On all fours（爬着）：
Infants are on all fours prior to learning to walk.

(14) At sixes and sevens（乱七八糟）：
Tony moved to a new office where everything is still at sixes and sevens.

(15) A nine days’ wonder（轰动一时但很快被遗忘的事）：
Helen became a popular singer, but suddenly she disappeared. Her singing career was only a nine days’ wonder.

(16) Nine times out of ten（多数情况下）：
Judith thought that students liked her very much, but nine times out of ten she was wrong.

(17)Ten to one（很可能）：
It is about 9 am. Ten to one, Christine will be late again for this morning’s meeting.

(18) A nine-to-five job（朝九晚五的工作）：
It is hard work to be a salesman but his work is freer than a nine-to-five job.

(19) One of those things（不可避免的不幸事）：
During a recession, the inability to get a good job is just one of those things in life

(20) One in a thousand（少有的人才）：
He relies a lot on his capable assistant, who is one in a thousand.