hard的形容词形式是hard；
hard
adj.坚固的;坚硬的;结实的;难做的;难懂的;难以回答的;困苦的;艰苦的;艰难的；；
adv.努力地;费力地;艰难地;猛力地;猛烈地;彻底认真地；
比较级 harder；最高级 hardest
Her job is hard work, but the pay is good.
她工作虽辛苦，但薪水不低。
When I left they were all still hard at it.
我离开的时候他们都还在努力工作。
You think you\'re really hard, don\'t you?
你是不是以为自己真的很勇猛？
