1. 力气;力量
    Energy is the ability and strength to do active physical things and the feeling that you are full of physical power and life.

energy

    e.g. He was saving his energy for next week's race in Belgium...
           他正为下周在比利时的比赛养精蓄锐。
    e.g. We try to boost our energy by eating.
           我们试图通过吃东西来增强体力。

2. 毅力；活力
    Energy is determination and enthusiasm about doing things.

    e.g. At 54 years old her energy and looks are magnificent...
           她54岁了，精力和气色都非常好。
    e.g. You have drive and energy for those things you are interested in.
           你对那些感兴趣的事情干劲十足。

3. 努力;精力
    Your energies are your efforts and attention, which you can direct towards a particular aim.

energy

    e.g. She had started to devote her energies to teaching rather than performing...
           她已经开始将精力从表演转移到教学中。
    e.g. We must concentrate our energies on treating addiction first.
           我们必须首先集中精力治疗毒瘾。

4. 能量;能源
    Energy is the power from sources such as electricity and coal that makes machines work or provides heat.

    e.g. ...those who favour nuclear energy...
           那些支持利用核能的人
    e.g. Oil shortages have brought on an energy crisis...
           石油短缺已经造成了能源危机。