一言为定的英文：
[Literal Meaning]
one/word/be/certain
to reach a binding agreement verbally

[解释]
一句话说定了，不再更改。

[Explanation]
That's settled.

[例子]
既然大家都同意周末去郊游，那我们就一言为定。

[Example]
Since everyone agreed to go for an outing this weekend, let's make this a promise.

[英文等价词]
That's a whack.
It's a deal.

`Certainly, from the keel to the truck of the masts, all the wood, that is.'
“当然了，当然了，一言为定，从上到下，所有‘木柴’，都归您！”

You got a deal.
一言为定。

I give you my word of honour
一言为定

TRENCH.(agreeably surprised)Then I suppose we may consider the affair as settled
屈兰奇:(喜出望外)那么我们就一言为定吧。

herbert was highly delighted when we shook hands on this arrangement
赫伯尔特万分高兴，我们握了握手，表示一言为定。

“You will be here at7:30tomorrow.”“All serene.”
“你明天早上7点半来这里。”“一言为定。”