万に一つ

• Reading: まんにひとつ
• Romaji: man ni hitotsu
• Kanji breakdown: 万 (man) — ten thousand; 一 (ichi/hito) — one
• Pronunciation: /maɴ.ni.çi.to.tsɯ/

Meaning

One in ten thousand; one in a million; in the unlikely event. Describes an extremely slim chance.

An expression functioning as an adverb or attributive adjective (with の). Used to describe an extremely unlikely possibility: 万に一つの可能性 (one-in-a-million chance). Often appears in conditional patterns: 万に一つでも (even if there's the slightest chance). Despite emphasising low probability, it is frequently used when that slim chance still matters and must be prepared for.

Examples

1. 万に一つの確率でも、備えておくべきだ。 Even if the odds are one in ten thousand, you should be prepared.
2. 成功する見込みは万に一つもないと思われていた。 The chances of success were thought to be virtually nonexistent.
3. 万に一つのことがあったら困るので保険に入った。 I got insurance just in case something unlikely but catastrophic happened.

Usage Guide

Context: risk assessment, insurance, cautionary talk

Tone: cautionary

Origin & History

From 万 (man, ten thousand) + に (ni, in/among) + 一つ (hitotsu, one). Literally 'one in ten thousand' — expressing the rarest of occurrences.

Cultural Context

Era: Classical origin

Generation: All ages

Social background: Universal