Duty, n.; pl. Duties.
Etymology: [From Due.]
1. That which is due; payment. [Obs. as signifying a material thing.] When thou receivest money for thy labor or ware, thou receivest thy duty. Tyndale.
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.
4. Specifically, obedience or submission due to parents and superiors. Shak.
6 more senses
5. Respect; reverence; regard; act of respect; homage. "My duty to you." Shak.
6. (Engin.)
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).
7. (Com.)
Tax, toll, impost, or customs; excise; any sum of money required by government to be paid on the importation, exportation, or consumption of goods.
Note: An impost on land or other real estate, and on the stock of farmers, is not called a duty, but a direct tax. [U.S.] 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.
Shades of meaning
Etymologically, duty is that which is owed or due; obligation, that to or by which one is bound; right, that which is correct, straight, or in the direct line of truth and goodness; responsibility, that for which one must answer. Duty and responsibility are thought of as to some person or persons; right is impersonal. One's duty may be to others or to himself; his obligations and responsibilities are to others. Duty arises from the nature of things; obligation and responsibility may be created by circumstances, as by one's own promise, or by the acceptance of a trust, etc. We speak of a parent's duty, a debtor's obligation; or of a child's duty of obedience, and a parent's responsibility for the child's welfare. Right is that which accords with the moral system of the universe. Righteousness is right incarnated in action. In a more limited sense, right may be used of what one may rightly claim, and so be the converse of duty. It is the creditor's right to demand payment, and the debtor's duty to pay. Compare business.