Three word expressions are common in English. Practicing them and using them when you speak will help you sound more natural. Here are several common expressions, along with an explanation and example sentence. black and white = something which is extremely clear（黑白分明的；绝对的）
He told her in black and white that she couldn't leave the house while he was out.
dos and don'ts = the rules （行为准则，须知，注意事项）
There are various dos and don'ts about driving in the UK.
haves and have nots = people who are rich and those who are not （富人和穷人）
In London you can find the haves and have nots of the population.
ins and outs = the details （细节，始末，详情）
I don't know the ins and outs of the situation, so I can't really advise you.
kiss and tell = when someone sells a story of themselves and a famous person （泄漏秘密）
The British tabloids are famous for publishing kiss and tell stories.
odds and ends = small pieces of various items （零碎东西，零星杂物）
She made a stew with the odds and ends she found in the fridge.
P's and Q's = manners ( such as please and thank you ) （言行）
Mind your P's and Q's when you visit them!
pros and cons = advantages and disadvantages （赞成和反对）
There are a few pros and cons that we should consider before buying a new house.
rights and wrongs = all the good points and bad points of a situation （事情的真相、全部）
Regardless of the rights and wrongs of company policy, you need to give a month's notice.
tried and tested = something which has been well tested （经过反复考验的）
Using salt is a tried and tested way of getting red wine out of a carpet.
ups and downs = good and bad periods following one another in turn（盛衰，沉浮）
They have a lot of ups and downs in their relationship.
back and forth = not to stay still, but to keep traveling between two places （来回地，反复地）
I'm so glad I'm moving. I was getting sick of going back and forth every day. Now my fourney to work will be a lot quicker.
dribs and drabs = small unimportant amounts （点滴、少量）
The marathon runners finished in dribs and drabs.
said and done = to have the final word on something （说到底，毕竟）
When it's all said and done, the new reception area is going to be a credit to the company.
cat and mouse = doing something in the same way that a cat plays with a mouse （猫鼠游戏，欲擒故纵）
The guerillas played a cat and mouse game with the much better-equipped army.
trial and error = to do something new by making experiments and occasionally falling 反复试验
The new computer system has been installed. But it's a bit trial and error at the moment - nobody really knows how to use it.
flesh and blood = your family 家人
I have to help him if I can - he's my flesh and blood.
down and out = someone who has no money at all who has to live on the street （贫困的，贫病交迫的）
There are too many young down and outs in London.
by and large = generally （大体上，总的说来，一般的说）
By and large, our customers prefer good service to low prices.
bring and buy = a fair where people try to raise money for a cause by bringing something that other people might want to buy （慈善救济性自由集市）
I'm making a cake for the school's bring and buy next week.
hide and seek = a children's game where one child hides and the others try to find him / her （捉迷藏）
Someone's been playing hide and seek with the TV remote control again.
to and fro = another way of saying " back and forth " （往返地，来回地）
I'm exhausted - I've been going to and fro all week!
over and out = something you say to show you have come to the end of your message （通话完毕）
The last thing they heard from the pilot was 'over and out'.
done and dusted = properly finished （完毕，了结）
Well, that's this project done and dusted. We need a holiday now.
wine and dine = to entertain someone lavishly （以好酒好菜款待客人）
He's well-known for winning and dining his business partners.
bread and butter = your main source of income, or the most important issue （维持生活所需的）
Health and education are the bread and butter issues facing the UK government.
spick and span = ( of a room, house, etc.) completely clean and tidy again （房间、屋子等打扫得干干净净的；整洁的）
Her house is spick and span at all times
wheel and deal = to make deals in a skillful and perhaps dishonest way when buying and selling things （讨价还价，玩弄手段，投机取巧）
If you need a new car, try speaking to John. He's a bit of a wheeler and dealer.

注：这里的‘don'ts’和“nots”很少用，可以理解为复数形式！