定义 / 说明
C2 的语域控制往往体现在“微小标记”上，而非明显语法差异。缩写、被动、情态缓和、立场表达、词汇层级、句长都会传递“随意/中性/礼貌/高度正式”。最高级能力是自然切换语域而不过火：正式不做作，非正式不粗糙。语域本质是精细校准。优秀使用者会按受众、目的和场景调整这些微标记。
关键规则
- 非正式/中性语境可更自由用缩写：I'm, it's, don't。
- 专业/学术语境常偏好全写、被动、正式立场短语：I regret to inform you。
- 按场景在短语动词与单词替代间选择：put off vs postpone。
- 语域不只是词汇，语法选择同样关键。
- 目标是风格一致，不要无理由混搭极正式与极口语。
例句
- I am afraid I cannot attend the meeting. - 很抱歉我无法参加会议。
- I regret to inform you that your application was unsuccessful. - 很遗憾通知您，您的申请未通过。
- We need to sort this out today. - 我们今天得把这事处理好。
- The meeting has been postponed until Monday. - 会议已推迟到周一。
- It would be appreciated if you replied by noon. - 如您能在中午前回复，将不胜感激。
常见错误
- ❌ I regret to tell you the party is off, mate. -> ✅ Keep one register: I regret to inform you ... / ✅ Sorry, the party is off ...
- ❌ The meeting was put off in a very formal report. -> ✅ The meeting was postponed in a formal report.
- ❌ I can't attend and therefore your request shall hereby be declined. -> ✅ Use one level consistently: I cannot attend, so I must decline your request.