Often used in military or security settings to describe someone on duty for observing and reporting. During the exercise, two cadets were assigned as sentries to monitor the perimeter.
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Vigilance Required
Implies a need for alertness and constant attention to the surroundings for possible threats. The role of the sentry is crucial; they must remain vigilant throughout their watch.
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Not Just Military
Can also refer to anyone assigned to keep watch in non-military contexts, like a guard at a museum. The museum's sentry kept a keen eye on visitors to prevent any art theft.