What does sentry mean?
A sentry is a person who stands guard at a particular place, watching for intruders, unauthorized entry, or other potential trouble. The role is especially associated with military bases, prisons, government buildings, and guarded facilities, though “sentry” can also be used more generally for any watchful lookout. The word carries a clear sense of vigilance and responsibility: the sentry is the person who remains alert while others rest or carry out their duties. Phrases such as “stand sentry,” “keep sentry duty,” and “sentry post” emphasize either the act of guarding or the location from which the watch is kept. Although “guard” is the ordinary everyday synonym, “sentry” remains useful because it specifically evokes a posted watch, often by an armed or uniformed person. It also extends figuratively to describe any person who keeps careful watch over a place, activity, or group.
A person stationed to guard a place, especially a member of an armed force who watches for unauthorized people or activity.
"The sentry challenged the driver and checked his credentials."
Most often used in military, law-enforcement, prison, and security settings.
The act or duty of keeping watch, or a person who performs that function.
"Two soldiers were assigned to sentry for the night."
This use is less common than the sense of an individual guard and can sound formal or literary.
The standard plural is “sentries.”
"The sentries changed shifts at midnight."
From battlefield lookout posts to modern security systems, the sentry has always represented the simple but vital idea of keeping watch.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does sentry come from?
The word entered English in the late 16th century, developed through French forms including sentinelle and older sentrie. It ultimately relates to Italian sentinella, from a Latin term associated with a watch or guard. English “sentinel,” French “sentinelle,” and Italian “sentinella” are related descendants of the same military and guard-related vocabulary.
How sentry is actually used
Sentry is most commonly used in military, police, prison, and security contexts. In general use, it may sound formal or literary, while “guard” is more neutral. The third sense, referring to the act of keeping watch, is less common in modern English.
Easily confused with sentry
A sentry is usually a person who physically guards a place, whereas a sentinel can refer either to a person or to an automated system that monitors and alerts to danger.
Sentry refers to a guard or lookout, while century refers to a period of one hundred years.