万无一失 wànwú-yìshī surefire
surefire; absolutely safe (idiom)
How to remember 万无一失: 万 ten thousand + 无 have not + 一 one + 失 to lose = surefire.
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How it is used
- Idiom: 'not one failure in ten thousand', i.e. absolutely foolproof - 做好准备，确保万无一失 (zuò hǎo zhǔnbèi, quèbǎo wànwú-yìshī) prepare thoroughly so nothing can go wrong.
- Used of plans and arrangements you want guaranteed safe; often after 确保/力求.