1．strength：力量，力气。常指固有的潜在力量，如人的气力、精力，也指物质的强度等。例如：

　 union is strength. 团结就是力量。

　 He lifted the stone with all his strength.

　 By doing so, you can test the strength of steel. 这样做，你可以试验一下钢的强度。

2．force：力量，力气。常指暴力、势力、军事力量等;复数形式指“兵力、武力”等。例如：

Finally they had to open the door by force.

It is the air force that matters. 是空中力量在起作用。

Air forces were sent to the front. 空军被派往前线。

3．energy：活力，精力，能量(指人的精力、自然界的能量等)。例如：

Jim is a man full of energy.

They are making use of solar energy. 他们在利用太阳能。

I’m afraid it’s a waste of energy by doing that.

4．power：力量，做事或行动的能力，指人或机器潜在的或发挥出来的力量；还可指职位、权力或政权等。例如：

Knowledge is power. 知识就是力量。

Water power is more enough in this area. 该地区水力资源丰富。

He has the power of life and death over thousands.他手中掌握有成千上万人的生死大权。

I’m sorry I can’t help you; it’s beyond my power.