on duty

Idioms  

1. At one's post, at work, as in The new nurse was on duty that evening, or The watchman was fired because he was drunk on duty. [Mid-1600s] The antonym, off duty, means “not engaged in one's work,” as in Captain Smith was much more amiable when he was off duty. [Mid-1800s]

---

Example Sentences

Rocket launches can be impacted by different 'weather rules' which need to be met before the launch weather officer on duty can give the 'go' decision on weather.

From BBC • Mar. 30, 2026

When asked whether there was only one controller on duty at the time of the crash, Duffy said that was false.

From The Wall Street Journal • Mar. 24, 2026

The accused include the station master on duty on the night of the accident, other railway officials and two Italian former employees of the trains' parent company, Ferrovie dello Stato.

From Barron's • Mar. 23, 2026

Battalion Chief Mario Garcia was on duty again that day.

From Los Angeles Times • Mar. 11, 2026

"How would you like it if it was you was on duty, or me? I'll not see anyone hurt."

From "Stardust" by Neil Gaiman