adjective describing the state of being engaged in work or official responsibilities
preposition indicating the location or position of being engaged in work or official responsibilities
Soldiers must always be on duty to protect their country.
Nurses and doctors take turns being on duty to provide round-the-clock care for patients.
Police officers are always on duty to ensure public safety.
Pilots and train conductors are on duty to safely transport passengers to their destinations.
Customer service representatives are on duty to assist customers with their inquiries and concerns.
Paramedics and firefighters are on duty to respond to emergencies and provide assistance.
Security guards are on duty to monitor and protect a premises from unauthorized access.
Police officers are on duty when they are actively working to enforce the law and protect the community.
Nurses are on duty when they are working their scheduled shifts in a hospital, clinic, or other healthcare setting.
Firefighters are on duty when they are at the fire station or responding to emergencies.
Security guards are on duty when they are monitoring and protecting a specific area or property.
Pilots are on duty when they are flying a plane and responsible for the safety of passengers and crew.