work hard play hard的意思是努力工作努力玩。hard主要用作為形容詞、副詞、名詞，作形容詞時意為“努力的；硬的；困難的；辛苦的；確實的；嚴厲的；猛烈的；冷酷無情的”，作副詞時意為“努力地；困難地；辛苦地；接地；猛烈地；牢固地”，作名詞時意為人名。

例句：

Why do they have to work so hard?

他們為什么工作必須那么努力。

Every one of us should work hard for the prosperity of our country.

我們每一個人都應該為我們國家的繁榮而努力工作。

I find it hard to trust not only me, but everyone around me, Because of.

因為你，我發現很難再相信我自己以及周圍的每一個人。

The ground is as hard as stone after the long drought.

長期干旱之后，土地硬得就像石頭一樣。

It's very hard to maintain a relationship.

要維持一段關系，是很困難的。

It's very hard on parents when their children are rebellious.

對父母來說，孩子叛逆是個很棘手的問題。