Duty

1. That which is due; payment.
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.
3. Hence, any assigned service or business; as, the duties of a policeman, or a soldier; to be on duty.
4. Specifically, obedience or submission due to parents and superiors.
5. Respect; reverence; regard; act of respect; homage.
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.
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.