What is "on duty"

Duty \Du"ty\, n.; pl. Duties. [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.

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. [1913 Webster] ||

alt. Actively engaged in an assigned task, duty or occupation. prep.phr. Actively engaged in an assigned task, duty or occupation.

adj. performing or scheduled for duties; "I'm on from five to midnight"; "Naval personnel on duty in Alaska"; "her on-duty hours were 11p.m. to 7 a.m." [syn: on(p), on duty(p), on-duty(a)]