Formal and informal speech are different registers, meaning different choices of words, grammar, and tone depending on the situation. Formal speech is used when you need distance, respect, or professionalism. Informal speech is used when you want friendliness, ease, or closeness. Good communication is choosing the register that fits the relationship, setting, and purpose.

Use formal language in professional messages, academic writing, official requests, customer service, and when speaking to someone you do not know well. Use informal language with friends, family, close coworkers, and casual online chat. When unsure, start formal and soften later if the other person writes informally or invites a more relaxed tone.

Formal speech often sounds more polite because it uses respectful framing, indirect requests, and careful wording. Informal speech can still be polite, but it is usually more direct and relaxed. In English, politeness is often created through modal verbs, softeners, and respectful phrases rather than special verb forms.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Use indirect requests to sound formal.	🧩 以间接请求来显得正式。	Could you please send the updated file by Friday?	🧩 您能否在周五前发送更新后的文件？
Use modals to soften and stay polite.	🧩 使用情态动词以缓和并保持礼貌。	Would you mind waiting a moment?	🧩 您介意稍等片刻吗？
Use direct imperatives mainly in informal contexts.	🧩 只在非正式场合使用直接祈使句。	Send me the file when you can.	🧩 当你有空时把文件发给我。
Add softeners for friendly informality.	🧩 为友好且非正式的语气添加缓和语气。	Just checking if you saw my message.	🧩 只是想确认你看到我的信息。

Formal English prefers precise, neutral, and sometimes Latinate vocabulary, while informal English prefers simpler, everyday words. The meaning may be similar, but the social effect changes: formal words create distance and professionalism; informal words create warmth and ease. Avoid slang, strong idioms, and texting shortcuts in formal contexts.

Word/Phrase	🇨🇳 中文 单词/短语	Definition	🇨🇳 中文 定义	Example	🇨🇳 中文 示例
purchase	🧩 采购	buy in a formal way	🧩 以正式方式购买	We plan to purchase new equipment.	🧩 我们计划购买新设备。
inquire	🧩 询问	ask for information formally	🧩 以正式方式请求信息	I am writing to inquire about availability.	🧩 我写信来咨询可用性。
assist	🧩 协助	help in a formal way	🧩 以正式方式提供帮助	Our staff can assist you.	🧩 我们的员工可以协助您。
request	🧩 请求	ask formally	🧩 正式请求	I would like to request a refund.	🧩 我想申请退款。
kids	🧩 孩子们	informal word for children	🧩 面向儿童的非正式词语	The kids are home from school.	🧩 孩子们放学回家了。
info	🧩 信息	informal short form of information	🧩 信息的非正式简写	Thanks for the info.	🧩 谢谢你的信息。

Contractions like I’m, don’t, and we’ve are common in informal speech and make writing sound conversational. Formal writing often avoids contractions to sound more neutral and careful, especially in academic or official documents. In many workplace emails, contractions are acceptable if the overall tone is professional.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Avoid contractions in very formal writing.	🧩 在极正式的写作中避免使用缩略形式。	We do not have sufficient information at this time.	🧩 目前我们没有足够的信息。
Use contractions for a friendly, natural tone.	🧩 为了获得友好、自然的语气而使用缩略形式。	We don’t have enough info yet.	🧩 我们还没有足够的信息。
Match the other person’s level of formality.	🧩 与对方的正式程度相匹配。	If they write I’m available, you can too.	🧩 如果他们写道 I’m available，你也可以。

Formal English tends to use longer, more structured sentences, clearer transitions, and full explanations. Informal English prefers shorter sentences, simpler connectors, and more implied context. Both can be clear; the difference is how much structure and explicitness you add.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Use explicit transitions in formal writing.	🧩 在正式写作中使用明确的过渡。	Therefore, we recommend postponing the launch.	🧩 因此，我们建议推迟启动。
Use simpler connectors in informal writing.	🧩 在非正式写作中使用更简单的连接词。	So I think we should wait.	🧩 所以我认为我们应该等待。
Prefer complete sentences in formal contexts.	🧩 在正式场景中偏好使用完整句。	I will review the document and respond tomorrow.	🧩 我将审阅文档并明天回复。
Fragments are common informally, especially in chat.	🧩 非正式场景常见片段句，尤其在聊天中。	Sounds good. Tomorrow works.	🧩 听起来不错。明天就行。

Requests are a key place where register matters because they can sound demanding or respectful. Formal requests often use could, would, may, and polite openings like I was wondering if. Informal requests often use can, want, or a simple imperative, especially with friends.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Use Could you or Would you in formal requests.	🧩 在正式请求中使用 Could you 或 Would you。	Would you be able to confirm receipt?	🧩 Would you be able to confirm receipt?
Use May I for very formal permission.	🧩 对于非常正式的许可使用 May I。	May I ask a quick question?	🧩 May I ask a quick question?
Use Can you in neutral to informal requests.	🧩 在中性至非正式的请求中使用 Can you。	Can you send it today?	🧩 Can you send it today?
Use imperatives with close relationships.	🧩 与亲密关系使用祈使句。	Let me know when you’re free.	🧩 Let me know when you’re free.

Openings and closings strongly signal formality in emails and letters. Formal greetings use Hello, Dear, or Good morning and often include titles and last names. Informal greetings use Hi and casual openings, and closings can be short or friendly. Choose a closing that matches the relationship and the seriousness of the message.

Word/Phrase	🇨🇳 中文 单词/短语	Definition	🇨🇳 中文 定义	Example	🇨🇳 中文 示例
Dear Ms. Patel	🧩 尊敬的 Patel 女士	formal greeting with title and surname	🧩 带有头衔与姓氏的正式问候	Dear Ms. Patel,	🧩 Patel 女士，
Hello Dr. Chen	🧩 陈博士，	formal to neutral greeting	🧩 从正式到中性问候	Hello Dr. Chen,	🧩 陈博士，
Hi Sam	🧩 嗨，山姆，	informal friendly greeting	🧩 非正式友好问候	Hi Sam,	🧩 Hi Sam,
Sincerely	🧩 此致，	formal closing	🧩 正式的结尾语	Sincerely, Jordan Lee	🧩 此致，Jordan Lee
Best regards	🧩 最诚挚的问候	professional but less formal closing	🧩 专业但不太正式的结尾	Best regards, Jordan	🧩 最诚挚的问候，Jordan
Thanks	🧩 谢谢	informal closing	🧩 非正式的结束语	Thanks, Jordan	🧩 谢谢，Jordan

Slang, strong idioms, and internet expressions create an informal voice and can confuse people who do not share the same background. In formal contexts, replace slang with clear literal language. In informal contexts, slang can build connection, but it can also sound unprofessional if the relationship is not close.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Avoid slang in formal communication.	🧩 在正式沟通中避免使用俚语。	The plan is not feasible at this time.	🧩 该计划在当前不可行。
Use literal language for clarity across audiences.	🧩 使用字面语言以便各受众理解。	We need to reduce costs by 10 percent.	🧩 我们需要将成本降低10%。
Use slang only with the right audience.	🧩 仅在合适的受众中使用俚语。	That meeting was pretty intense.	🧩 那次会议相当激烈。

You can shift between formal and informal speech by changing a few high-impact signals: greeting, contractions, word choice, and request style. Softening or strengthening formality helps you manage relationship and authority without changing the message. Aim for consistency so the tone does not feel mixed or confusing.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
To become more formal, remove contractions and add polite modals.	🧩 要变得更正式，请去除缩略形式并添加礼貌情态动词。	Could you please review the report?	🧩 Could you please review the report?
To become more informal, shorten and use everyday words.	🧩 要变得更非正式，请缩短并使用日常词汇。	Can you take a look at the report?	🧩 Can you take a look at the report?
Keep formality consistent from greeting to closing.	🧩 从问候到结束保持正式程度的一致性。	Hello Ms. Rivera ... Best regards	🧩 你好 Rivera 女士……此致，敬礼