说定的英文：
agree on; settle

参考例句：

That's all right
就这样说定。

She hasn't yet titled her novel.
她还没有给她的小说定篇题。

agree是什么意思：
v. 商定，约定；同意；赞成；承认；一致；符合；适宜

The day after, she agreed.
一天之后，她同意了。

Birds in their little nests agree
同巢之鸟相处好;家和万事兴

Friends agree best at distance
君子之交淡如水

My lawyer will agree with the transaction.
我的律师将同意这份和解协议。

Two of a trade seldom agree
同行是冤家

settle是什么意思：
v. （使）定居，安定；解决；安排；沉淀；下陷

It was settled by lot.
这事是以抽签决定的。

It was settled by lotting.
这事是以抽签决定的。

No question is ever settled until it is settled right
正确解决问题才算真正解决

Alum will settle turbid water.
明矾可以澄清浊水。

Settle down or stay, as if on a roost.
安歇或暂住，好像在栖息所。