Origin: From Due.
2. That which a person is bound by moral obligation to do, or refrain from doing; that which one ought to do; service morally obligatory. Forgetting his duty toward god, his sovereign lord, and his country. (Hallam)
3. Hence, any assigned service or business; as, the duties of a policeman, or a soldier; to be on duty. With records sweet of duties done. (Keble) To employ him on the hardest and most imperative duty. (Hallam) Duty is a graver term than obligation. A duty hardly exists to do trivial things; but there may be an obligation to do them. (c. J. Smith)
6. (Science: engineering) The efficiency of an engine, especially a steam pumping engine, as measured by work done by a certain quantity of fuel; usually, the number of pounds of water lifted one foot by one bushel of coal (94 lbs. Old standard), or by 1 cwt. (112 lbs, England, or 100 lbs, united States).
An impost on land or other real estate, and on the stock of farmers, is not called a duty, but a direct tax. Ad valorem duty, a duty which is graded according to the cost, or market value, of the article taxed. See ad valorem. Specific duty, a duty of a specific sum assessed on an article without reference to its value or market. On duty, actually engaged in the performance of one's assigned task.