In algebra, the sign X usually denotes an unknown quantity.

在代数里, 符号X常用来表示未知数。

Our new director is still an unknown quantity.

我们对新来主管知之甚少。

Motherhood was for her a journey into the unknown.

做母对她来说是开始一次探险之旅。

He lived well, helping the poor, and all other people; he died penniless and unknown.

他生前讲道德, 总是帮助穷人以及所有人; 后来却一文不名, 默默无闻地死了。

The origins of some words are unknown.

这些词起源是不知。

Some Austrians, ungratefully, nicknamed it the “Looter's memorial” or the “Unknown rapist”.

一些奥地利人不仅不心怀感激，并且将它称之为“侵略者纪念馆”或者“不为人知强奸犯”。

Life can be likened to a journey with an unknown destination.

生活可以被比作一次不知目旅行。

The championship was won by a complete unknown.

一个名不见经传人赢得了冠军。

Their football team bowed out of the competition with unknown reasons.

不知道为什么他们足球队退了比赛。

Those explorers gallantly adventured on unknown seas.

那些探险家们大胆地在陌生海域探险。

People usually infer an unknown fact from a known fact.

人们通常从已知事实中推断未知事实。

Yesterday’s riot broke out at the instigation of an unknown politician.

昨日暴乱是由一个不知名政客煽动起来。

An unknown man's dismembered body was found by the police in the suburb woods.

警察在郊区小森林里发现了一个不知名男人碎尸。

Unknown to me, he had already signed the agreement.

他背着我已签了协议。

An unknown man has stolen all her money.

一个陌生人把她钱偷光了。

She was then still comparatively unknown.

她那候还不怎么名。

The cause of autism is unknown.

自闭症病因尚不清楚。

Those who dared to launch out beyond the unknown waters became the discoverers of new lands.

那些敢于去人迹未至海域航行人成了新陆地发现者。

There are many unknowns in science.

科学上还有许多未知之处。

It was unknown country to me.

这地区对我说来是陌生。