万无一失

• Pinyin: wàn wú yī shī
• Hanzi breakdown: 万 = ten thousand; 无 = pictograph of a dancer — absence; 一 = one (horizontal stroke); 失 = 手 (hand) + 乙 (twist) — to let slip from the hand

Meaning

Absolutely foolproof; with no possibility of failure; not a single thing can go wrong. Describes a plan or arrangement that is entirely safe and certain to succeed.

A four-character idiom (成语). Used to describe a plan, measure, or arrangement that has been so thoroughly prepared that failure is impossible. Often used in reassurance ('everything is taken care of') or in tactical planning. Can be used sincerely or ironically.

Examples

1. 安保人员对每个细节都进行了反复核查，确保万无一失。 The security personnel repeatedly checked every detail to ensure there was absolutely no room for failure.
2. 他声称计划万无一失，但实施时还是出现了意外。 He claimed the plan was foolproof, but when it was implemented, the unexpected still happened.
3. 这次手术风险较高，医生做了充分准备，力求万无一失。 This surgery carries significant risk; the doctors made thorough preparations striving for absolute certainty.

Usage Guide

Context: planning, security, reassurance

Tone: confident

Do Say

• 我们已经做好了充分的准备，力保万无一失。(We have made thorough preparations to ensure there is absolutely no room for error.)
• 虽然他说计划万无一失，我还是建议准备一个备用方案。(Although he says the plan is foolproof, I still recommend preparing a backup.)

Don't Say

• 将万无一失用于描述已经失败的事情 — the phrase only fits prospective planning or reassurance, not retrospective assessment of what went wrong

Origin & History

万 (ten thousand) + 无 (without) + 一 (one) + 失 (loss, failure). Literally 'ten thousand without a single failure' — absolute certainty with no room for error.

Cultural Context

Generation: All ages

Social background: Universal