http://zhidao.baidu.com/question/16608998.html?fr=qrl&fr2=query&adt=0_951 Success comes from hard work , so we must work hard.

hard work is self discipline. eg. Patience and hard work are two of the important attitudes toward success. work hard is jia you in chinese.

sorry， hard work中，work是名词。

前一个phrase，hard是形容词，work是动词， 后面的phrase， work是动词，hard 是副词。