Translation guide
A sentinel is a guard or lookout who keeps watch. In Japanese, this can be expressed with words for guard, lookout, or watchman, depending on the context.
A person assigned to keep watch and protect a place
A military sentinel or sentry on foot patrol. Commonly used in military contexts.
A sentinel was standing guard at the gate.
A guard or sentry, often used for a soldier on guard duty.
The sentinel kept watch all night.
A lookout or watchman; can be used for a sentinel in a general sense, not necessarily military.
A sentinel stood on top of the tower.
A palace or ceremonial guard; more formal and often associated with royal or official settings.
The sentinel guarded the palace entrance.
Something that stands as a protector or warning sign
歩哨 (hoshō) is specifically a military sentinel on foot patrol. 番兵 (banpei) is a general guard or sentry, often military. 見張り (mihari) is a lookout or watchman, used in both military and non-military contexts. For a civilian guard, 見張り is more natural.
Directly translating 'sentinel' as センチネル (senchineru) is a loanword used mainly in specific contexts like programming or brand names, not for a guard. Use the Japanese terms above for a person or figurative guardian.
The old tree stood on the hill like a sentinel.