yì一oneyán言wordwéi为makedìng定settled
One word and it's settled — done deal.
Literal meaning
one (一) — word (言) — make (为) — settled (定)
Origin
A traditional four-character phrase capturing the Confucian respect for a person's word. Saying 一言为定 to seal an agreement was the cultural equivalent of shaking hands. Still common in modern Chinese spoken and written commitments.
Examples
Míng明tiān天xià下wǔ午liǎng两diǎn点jiàn见，yì一yán言wéi为dìng定。
See you tomorrow at 2pm — it's a deal.
Wǒ我men们yì一yán言wéi为dìng定，bú不zài再gǎi改le了。
We've settled it — no more changes.
Usage & nuances
Casual, common. Used to lock in any agreement, formal or informal.
Learn idioms by speaking them
Idioms are most useful when they land in a real conversation. Practice them out loud in Kango — get instant feedback on tone and timing.
Download Kango on iOS