关于duty的用法与搭配结构

　　1. 表示有责任或义务做某事，其后可接 to do sth 或 of doing sth。如：

A man has a duty to earn money for his family. 男人有挣钱养家的责任。

Every citizen has the duty of defending his country. 每个公民都有保卫祖国的责任。

　　2. 表示“责任”“义务”，视含义的具体或抽象可用作可数或不可数名词。如：

Everyone has a duty to his country. 为国效劳，人人有责。

He did it out of a sense of duty. 他做此事是出于一种责任感。

表示作为工作一部分的“职责”或“职务”等，通常用复数形式。如：

Don’t forget your duties as a soldier. 不要忘记你作为一名战士的职责。

Your duties include checking the post and distributing it. 你的职责是检查和发送邮件。

　　3. 比较 do duty for sb(代替某人)与 do duty for sth(充当或当作某物用)。如：

He did duty for a sick comrade. 他接替一位患病的同志工作。

An old wooden box did duty for a table. 一个旧木箱子被当作桌子用。

　　4. 用于 on (off) duty, 意为“值(值)班”“当(不当)班”等(注意不用冠词)。如：

He goes on duty at 8 am and comes off duty at 5 pm. 他上午8点上班下午5点下班。

The rule is that someone must be on duty at all times. 按照规定，任何时候均需有人值班。