duty

(noun): That which one is morally or legally obligated to do.
(noun): The state of being at work and responsible for or doing a particular task.
(noun): A tax placed on imports or exports; a tariff.
(noun): One's due, something one is owed; a debt or fee.
(noun): Respect; reverence; regard; act of respect; homage.
(noun): 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).