Duty

A legal obligation that entails mandatory conduct or performance. With respect to the laws relating to Customs Duties, a tax owed to the government for the import or export of goods.

A fiduciary, such as an executor or trustee, who occupies a position of confidence in relation to a third person, owes such person a duty to render services, provide care, or perform certain acts on his or her behalf.

In the context of Negligence cases, a person has a duty to comport himself or herself in a particular manner with respect to another person.

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duty n. 1) a legal obligation, the breach of which can result in liability. In a lawsuit a plaintiff must claim and prove that there was a duty by defendant to plaintiff. This can be a duty of care in a negligence case or a duty to perform in a contract case. 2) a tax on imports. (See: duty of care)

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DUTY, natural law. A human action which is, exactly conformable to the laws which require us to obey them.
     2. It differs from a legal obligation, because a duty cannot always be enforced by the law; it is our duty, for example, to be temperate in eating, but we are under no legal obligation to be so; we ought to love our neighbors, but no law obliges us to love them.
     3. Duties may be considered in the relation of man towards God, towards himself, and towards mankind. 1. We are bound to obey the will of God as far as we are able to discover it, because he is the sovereign Lord of the universe who made and governs all things by his almighty power, and infinite wisdom. The general name of this duty is piety: which consists in entertaining just opinions concerning him, and partly in such affections towards him, and such, worship of him, as is suitable to these opinions.
     4.-2. A man has a duty to perform towards himself; he is bound by the law of nature to protect his life and his limbs; it is his duty, too, to avoid all intemperance in eating and drinking, and in the unlawful gratification of all his other appetites.
     5.-3. He has duties to perform towards others. He is bound to do to others the same justice which he would have a right to expect them to do to him.