正式英文 vs 非正式英文 | Formal vs Informal English: 30 Key Pairs

When you apply for a job in Taiwan, the recruiter reads your English email and makes a judgment in about 30 seconds. If you write “Hey, I wanna know if the position is still open,” the call probably never happens. Writing “Dear Ms. Chen, I would like to inquire about the current status of the advertised position” signals something completely different: respect, education, and awareness of context.

The gap between those two sentences is called register — and it is one of the most overlooked skills in English education in Taiwan. Most learners spend years on grammar rules without learning WHY the same word or sentence can be perfect in one situation and wrong in another. This guide covers the 30 most useful formal vs informal English pairs, along with the grammar patterns, email phrases, and common mistakes that separate fluent speakers from advanced ones.

什麼是語域 (Register)? [What Is Language Register?]

Register sounds like a technical term, but the concept is simple: different social contexts require different kinds of language. A text to your best friend and a report to your manager might carry the same information, but they should never sound the same.

There are two main registers in English:

• Formal register: professional emails, job applications, academic writing, business reports, speeches, presentations
• Informal register: text messages, social media, casual conversation, messages to friends and family

You already do this automatically in Chinese — 您好 vs 你好, or 請問 vs 喂. English works the same way. The problem is that many Taiwanese learners default to one style for all situations, which can come across as either too stiff or disrespectful depending on the context.

Knowing which English register to use — formal or informal — is an essential skill for Taiwan’s bilingual workforce.

正式英文 vs 非正式英文：30 個必學詞彙對比 [Formal vs Informal: 30 Key Vocabulary Pairs]

The most visible difference between formal and informal English is vocabulary. Native speakers switch between these word pairs automatically — usually without thinking about it. Learning them deliberately gives you that same control.

Professional emails are one of the clearest contexts where formal vs informal English vocabulary makes a measurable difference.

These word pairs add up fast. A single email that mixes informal words into a formal context — “I wanna touch base about the meeting, gonna send you the report ASAP” — signals to any fluent reader that something is off. None of those mistakes are grammar errors; they are all register errors.

正式英文的文法特徵 [Grammar Patterns in Formal English]

Vocabulary is the most obvious layer, but formal English also follows distinct grammar patterns. These are not strict rules — native speakers bend them constantly in spoken language — but in written formal contexts they matter.

Contractions (縮寫): formal English avoids them entirely.

• Informal: “It’s not possible.”
• Formal: “It is not possible.”

Passive voice (被動語態): formal writing uses it heavily to sound objective and impersonal. Passive constructions remove the actor from the sentence, which is often the point in business and academic writing. Instead of “We delayed the shipment,” formal writing says “The shipment was delayed.” For a full breakdown of when and how to use this, see our 英文被動語態 (Passive Voice) guide.

Complete sentences: informal conversation is full of fragments — “Sure.” “Maybe.” “Let me check.” Formal writing requires a subject and verb in every sentence.

Sentence-initial conjunctions: starting a sentence with “And” or “But” is natural in speech and increasingly accepted in writing. In formal reports and professional emails, though, replace these with “In addition” or “However.”

In a job interview or formal business meeting, using the right English register signals education and professionalism.

電子郵件開頭和結尾 [Formal vs Informal Email Openings and Closings]

Email is where register mistakes are most visible — and most costly. Here is what the difference looks like across the three main levels:

Openings (開頭):

Introducing the purpose (說明來信目的):

Closings (結尾):

One rule most Taiwanese learners miss: “Yours sincerely” is used when you know the recipient’s name. “Yours faithfully” is used when you open with “To Whom It May Concern” and do not know the person’s name. They are not interchangeable, and native readers notice the difference.

For a complete set of workplace English phrases including meeting openings, disagreements, and follow-ups, see the 會議英文 (Meeting English) guide.

Informal English is natural and warm — and perfectly appropriate when the context calls for it. The key is knowing when that is.

台灣學生最常犯的 5 個語域錯誤 [5 Register Mistakes Taiwan Learners Make Most]

These five errors come up constantly in Taiwan’s professional English environment.

1. “I want to…” in formal requests
“I want” is direct to the point of sounding rude in professional contexts. Replace with “I would like to…” or “I would be grateful if…” The distance between “I want a refund” and “I would like to request a refund” is not about grammar — it is about register.

2. Contractions in job applications
“I’m confident I’d be an excellent fit” should be “I am confident I would be an excellent fit” in any formal document. Every contraction in a job application or official report reads as informal.

3. Abbreviations in professional emails
“ASAP,” “FYI,” “BTW,” and “TBH” are fine in Slack with a colleague you know. In an email to a client, a recruiter, or anyone you do not have a casual relationship with, write the full phrase: “as soon as possible,” “for your information,” “by the way,” “to be honest.”

4. Starting professional emails with “Hey”
Even in American English, “Hey” is casual. When emailing someone you do not know well — a recruiter, a client, a professor — use “Dear” or at minimum “Hi.” The word “Hey” at the start of a cold email is the fastest way to kill the impression you are trying to make.

5. Over-formality in casual situations
The reverse problem also happens. Some learners apply formal English to every situation, which makes casual conversation feel stiff and awkward. You do not need “I would be most grateful” in a WhatsApp message to a friend. Reading the room — knowing when to drop the formal register — is a skill too.

Studying English register is about learning which words and structures belong in which context — not just memorizing vocabulary.

快速參考表 — 什麼情境用什麼語域 [Quick Reference: Which Register for Which Context?]

Preparing for IELTS or TOEFL? Academic writing is deeply tied to formal register. The IELTS / TOEFL academic vocabulary guide goes deeper into the vocabulary patterns that score well on the writing sections.

觀看影片學更多 [Watch This Lesson to Learn More]

The BBC English Masterclass series is one of the best free resources for understanding English register. This lesson walks through real examples of formal and informal English and explains the underlying logic clearly:

練習題 [Practice Exercises: Switch the Register]

Take each informal sentence below and rewrite it in a formal style. A suggested answer follows each one.

Exercise 1: “Gonna send you the report by Friday.”
Formal: “I will submit the report by Friday.”

Exercise 2: “Can’t make the meeting tomorrow — something came up.”
Formal: “Unfortunately, I will not be able to attend tomorrow’s meeting due to a prior commitment.”

Exercise 3: “Let me know ASAP.”
Formal: “Please respond at your earliest convenience.”

Exercise 4: “I wanna work at your company.”
Formal: “I would like to apply for a position at your organization.”

Exercise 5: “The boss said we gotta redo the whole report.”
Formal: “We have been informed that the report requires a full revision.”

Practicing formal English rewriting exercises builds the automatic register-switching skill that fluent speakers use every day.

If you got four or five correct, your register awareness is already strong. If you found the exercise difficult, go back to the vocabulary table and focus on the most common substitutions — those ten to fifteen pairs account for the majority of formal writing in Taiwan’s business context.

語域是讓英文更有說服力的關鍵 [Register Is What Makes Your English Count]

Most Taiwanese English learners hit a ceiling where they can communicate clearly but cannot control the impression they make. Register is what closes that gap. The good news: you do not need a completely different vocabulary — you need to learn when to swap maybe 30 to 50 words and a handful of grammar patterns.

The practical exercise that works best: pick any topic and write two short paragraphs about it — one to a friend via text, one as a professional email. Notice the specific words and structures you change. Those are your register signals. Over time, switching becomes automatic.

Informal English with friends is natural and important — the goal is not to eliminate it, but to know when to switch.

Building a vocabulary of formal vs informal word pairs gives you deliberate control over your English register.

แหล่งที่มา

1. BBC Learning English — English Masterclass: Formal and Informal English — Comprehensive guide to formal and informal register with real examples.
2. British Council — Formal or Informal? Top Tips for Choosing the Right Register — Guidance on selecting the appropriate English register for different contexts.
3. British Council LearnEnglish — Formal and Informal Language (B1–B2 Grammar) — Grammar reference for formal vs informal English at intermediate to upper-intermediate level.