Formal and Informal Styles
Generally speaking,letters,reports,proposals,legal documents,and brochures are always written in a formal style,and advertisement leaflets,memos,sticky notes,and e-mails are written in an informal style.For examples:
[4]Dear( ):
Your loved ones must be noticing.We are too.
It's been almost a year since you ordered flowers for delivery from(Fabulous Flores).You've been such a good customer that this realization surprised us and prompted us to inquire if there was something we did.If so,we'd like to make amends.
We hope you'll be in touch.In the meantime,mention this letter when you place your next delivery order and we'll take 15 percent off.
Please do call or come in soon.We really appreciate your business.
Sincerely,
We can make a comparison between the above letter and the following letter:
[5]Dear Sirs:
Our new-factory will be commencing production on April 10 and we would like to invite you and your wife to be present at a celebration to mark the occasion.
As you know,it is an important milestone for our company,resulting from the increasing demand for our products both at home and overseas.We are inviting all those individuals and firms that have contributed to our success,and believe that you will pay us the compliment of accepting.
The luncheon will be arranged at the Grand Hotel,followed by the opening ceremony and a tour of the factory.In the evening there will be a banquet at the same hotel.Please confirm that you will be able to attend by informing us of your arrival time—we can arrange for you to be met.We will pay for all the arrangements for your stay overnight on the 15 th. Best wishes.
Through the comparison between these two letters,some distinctions between formal style and informal style can be recognized.
3.1 Contractions
Informal languages prefer to use contraction,which makes the tone more conversational and personal.In this way,the gap between readers and writers can be narrowed down.On the contrary,formal language does not use contractions.
In formal languages,polysyllabic words are used more commonly than monosyllabic words or phrases.For examples:

continued

3.2 Phrasal verbs
Phrasal verbs always appear in the informal writings and the corresponding verbs are often used in formal writings.In the first letter,there are several collocations,such as in touch,take off,and come in.Their corresponding verbs can be contact,discount and visit.
3.3 Sentence Structure
In the first letter,there are nine sentences and most of them are short.The average length of the following sentences is 3 to 8 words.In some cases,Omission or replacement is used.
In the second letter,there are seven sentences and most of them are long.The average length of the following sentences is 20 to 29 words and each sentence is complicated.
Notes
propaganda 宣传
socialize 交际
questionnaires 问卷调查
feasibility reports 可行性报告
company profiles 公司简介
manuals 手册
letters of attorney 委任书
application forms 申请书
social etiquette 社交礼仪
letter of consolation 慰问信
message of condolences 唁电
message slip 留言条
receipt for a loan 欠条
ambiguous 引起歧义的
fuzzy 模糊的
modifiers 修饰语
acronyms 首字母缩写
jargons 行话
WTO(World Trade Organization) 世贸组织
WCO(World Customs Organization) 世界海关组织
sepsis 败血症
complications 并发症
computerized tomography 计算机X线断层摄影术
bonded 保税的
consignment 寄售货物
freight forwarding 货运代理
completely knocked down(CKD) 全拆卸
patented 专利
fuel filtering 燃料过滤
noxious 有毒的
combustion engines 内燃发动机
overhaul 彻底检修
manifold assembly 多样式组合
carburetors 化油器
wordy 冗长的
sensor 传感器
textured 有纹理的,质地粗糙的
ridge 脊
lading system 转载系统
rinse 清洗
fellow camper 游客
harsh 严厉的
sexism 性别歧视
brochures 小册子
leaflet 传单