duty

Etymology

From Middle English duete, from Middle English dewe) + Middle English -te, (borrowed from Old French -te from Latin -tātem, accusative masculine singular of -tās). Equivalent to due + -ty (Alternative form of -ity).

noun

1. That which one is morally or legally obligated to do.
   We don't have a duty to keep you here.
   1805, 21 October, Horatio Nelson England expects that every man will do his duty.
   Charles had not been employed above six months at Darracott Place, but he was not such a whopstraw as to make the least noise in the performance of his duties when his lordship was out of humour. 1959, Georgette Heyer, chapter 1, in The Unknown Ajax
   British journalists shun complete respectability, feeling a duty to be ready to savage the mighty, or rummage through their bins. Elsewhere in Europe, government contracts and subsidies ensure that press barons will only defy the mighty so far. 2013-08-10, Lexington, “Keeping the mighty honest”, in The Economist, volume 408, number 8848
2. The state of being at work and responsible for or doing a particular task.
   I’m on duty from 6 pm to 6 am.
3. A tax placed on imports or exports; a tariff.
   customs duty; excise duty
4. (obsolete) One's due, something one is owed; a debt or fee.
5. (obsolete) Respect; reverence; regard; act of respect; homage.
6. 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).