work hard和hard work的含义不同、词性不同、形容的对象不同。work hard意思是努力学习、辛勤工作，这里的work是动词，hard是副词，用来形容人工作很努力。hard work意思是努力工作、繁重的工作，这里的work是名词，hard是形容词，用来形容工作比较困难、繁重。

She complained that he did not work hard.

她抱怨他工作不努力。

She is very tenacious and will work hard and long to achieve objectives

她是个锲而不舍的人，为了达到目标愿意长期苦干。

The president will have to work hard to restore his credibility.

总统将不得不努力使公众恢复对他的信任。

Everyone would have to work hard together to rebuild the economy

所有人都应该一起努力以重建经济。

The Government will have to work hard to win back the confidence of the people

政府必须勤奋工作以重新赢得人民的信任。

Magicians do not dabble, they work hard.

魔术师可不是随便玩两下的，他们下了苦功钻研。