duty, obligation, responsibility

　　duty n.指道义上的责任，强调自觉性，作可数名词时指本职工作的任务。

　　His duty is to see that the business runs well.他的职责是保证生意良好运转。

　　obligation n.指合同或法律上规定的责任，义务，强调其约束力。

　　Parents have a legal obligation to ensure that their children are provided with efficient education suitable to their age.父母有法律上的义务确保其子女受到适合其年龄的有效教育。

　　responsibility n.职责，强调对后果要负责任的意思。

　　His father is ill, and he has the responsibility of caring for him.他的父亲病了，他有责任照顾他。