hard可以用作形容词，作“困难的”解时,指要消耗很大的体力去做某事,有时也指精神上的困难。hard可以用作副词，修饰动态动词,位于实义动词之后。

一.hard可以用作形容词

1.hard作“困难的”解时,指要消耗很大的体力去做某事,有时也指精神上的困难。hard还可表示“费力的,费神的,艰难的” “持强硬态度的,不妥协的,不让步的” “有力的,猛烈的,严厉的” “困苦的,难以忍受的” “(声音)刺耳的,(颜色)刺目的” “酒精含量高的”等。

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

长期干旱之后,土地硬得就像石头一样。

It's very hard to maintain a relationship.要维持一段关系,是很困难的。

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

对父母来说,孩子叛逆是个很棘手的问题。

2.hard在句中可用作定语或表语,其后可跟for〔to, with〕等介词短语、动词不定式、that从句。

二.hard可以用作副词

1.hard修饰动态动词,位于实义动词之后。hard一般表示“困难的”。

This is a hard question to answer.这是个难题，不好回答。

2.hard在hard of hearing（有些聋的）中有特殊含义“艰难的”

Most importantly, you must work hard to catch up.

最为重要的是,你必须努力学习,迎头赶上。

The senator was hard opposed by her rivals on the issue of social welfare.

那名参议员在社会福利问题上遭到对手强烈的反对。

Small businesses in particular were hit hard by the recession.

尤其是一些小企业在经济萧条中遭受了严重的打击。