"unknown quantity" in Chinese (Simplified)
未知数未知的人物
Definition
一种能力、影响或结果尚未得知的人或事物；也指因信息不足而不可预测的事物。
Usage Notes (Chinese (Simplified))
多为半正式表达，常用于形容未知影响的人或事。可形容新人、竞争者或不确定的因素。一般日常语境下不指数学上的“未知数”。
Examples
Until we see him play, he's really just an unknown quantity.
在我们看到他表现之前，他真的只是个**未知数**。
The new teacher is still an unknown quantity to us.
新老师对我们来说仍然是个**未知数**。
He is an unknown quantity in this competition.
他在这场比赛中是个**未知数**。
The weather is always an unknown quantity here.
这里的天气总是个**未知数**。
Bringing in a player from another country can be an unknown quantity for the team.
从国外引进一名球员对球队来说可能是个**未知数**。
How the new policy will work out is still an unknown quantity.
新政策会如何实施仍然是个**未知数**。