一经

• Pinyin: yī jīng
• Hanzi breakdown: 一 = once/one; 经 = 纟 + 巠 (silk thread + phonetic — threads on a loom; to pass through, to undergo)

Meaning

Once; as soon as; upon (doing something). An adverb introducing a conditional clause: once a particular action occurs or condition is met, the stated consequence immediately follows.

Structure: 一经 + [verb phrase] + [consequence clause]. Emphasises that the consequence is automatic and immediate once the condition is fulfilled. Common in legal, official, and formal contexts: 一经发现 (once discovered), 一经核实 (once verified), 一经录用 (upon acceptance of employment). Implies no further deliberation is needed after the condition is met.

Examples

1. 申请材料一经提交便无法修改，请在提交前仔细核对所有信息是否准确完整。 Once the application materials are submitted, they can’t be changed. Please double-check that all information is accurate and complete before submitting.
2. 此规定一经公布立即生效，所有相关部门须于五个工作日内完成内部政策的相应调整。 Once this regulation is announced, it takes effect immediately. All relevant departments must complete corresponding internal policy adjustments within five business days.
3. 产品一经上市便受到了消费者的热烈欢迎，首批库存在发售后四十八小时内便告售罄。 Once the product hit the market, it was warmly welcomed by consumers, and the first batch sold out within forty-eight hours.

Usage Guide

Context: legal, official, business, announcement

Tone: authoritative

Do Say

• 根据公司保密协议，员工在职期间所接触的所有商业机密信息一经外泄，相关责任人将立即承担民事赔偿责任，情节严重者另行追究刑事责任。(According to the company's non-disclosure agreement, any commercial secrets accessed by employees — once leaked — shall immediately trigger civil compensation liability for the responsible party; those involving serious circumstances shall additionally face criminal prosecution.)
• 该软件系统一经激活便会自动与云端服务器同步，用户的所有设置偏好与历史数据将在新设备上无缝恢复，无需任何手动导入操作。(Once this software system is activated, it automatically synchronises with the cloud server; all the user's settings and historical data will be seamlessly restored on a new device without any manual import operations.)

Don't Say

• 他一经走路就很快 — 一经 introduces a conditional clause requiring a consequence to follow; it cannot simply modify the manner of an ongoing action; use 他走路一向很快 instead

Origin & History

一 (once/one instance) + 经 (to pass through/undergo — 纟 silk thread + 巠 phonetic; threads on a loom, extended to 'to go through,' 'once having passed through')

Cultural Context

Era: Modern

Generation: All ages

Social background: Universal