to ask for something forcefully, in a way that shows that you do not expect to be refused

I demanded an explanation. 我要求给我一个解释。

The union is demanding a seven percent pay rise this year. 工会要求今年加薪7%。

He has always demanded the highest standards of behaviour from his children. 他总是以最高的行为准则来要求自己的孩子。

[ + speech ] "And where do you think you're going?" demanded the police officer. “你觉得自己在朝哪里走？”警察问道。

[ + to infinitive ] I demand to see the manager. 我要求见经理。

[ + that ] She demanded that he return the books he borrowed from her. 她要求他把从她那里借走的书还回来。

to need something such as time, effort, or a particular quality

This is a very difficult piece of music to play - it demands a lot of concentration. 这段乐曲很难演奏——需要注意力高度集中。

He seems to lack many of the qualities demanded of (= needed by) a successful politician. 他似乎缺少成功政治家所应具备的很多素质。

a strong request

You can't give in to children's demands all the time. 你不能总是对孩子们的要求作出让步。

The government is unlikely to agree to the rebels' demands for independence. 政府不可能同意叛乱者提出的独立要求。

UK They received a final demand (= a last request) for payment. 他们收到了要求付款的最后通牒。

a need for something to be sold or supplied

There was little demand for tickets. 很少有人来买票。

Good teachers are always in (great) demand (= are always needed). 社会总是需要（大量的）优秀教师。

the difficult things that you have to do

The demands of nursing are too great for a lot of people. 护理工作的要求之高令很多人都难以承受。

His new job makes a lot of demands on him (= he has to work very hard). 新工作对他要求很高。

The long hours and the physical demands of the work are driving people away from the profession.

Many struggle with the conflicting demands of work and family.

on demandidiom 一经要求，在有需求时