A sentinel is a sentry: a person, usually a soldier, who stands watch and looks out for danger. The word is a little more formal or story-like than sentry; in a novel a sentinel stands at the gate, in the army you may just say sentry.

A sentinel is a sentrysentinel 是哨兵：a person, usually a soldier一個人，通常是士兵，who stands watch負責站哨 and looks out for danger留意危險。The word is a little more formal or story-like than sentry這個字比 sentry 更正式、也更有故事感一點；in a novel a sentinel stands at the gate在小說裡 sentinel 會站在門口，in the army you may just say sentry在軍隊裡你可能就只會說 sentry。

People stretch it. A lighthouse can be a sentinel on a coast.

People stretch it人們把這個字延伸使用。A lighthouse can be a sentinel on a coast燈塔可以是海岸上的 sentinel（守望者）。

In science, a sentinel species is an animal whose trouble warns us that the place is sick; in medicine a sentinel node is the first lymph node doctors check. Those are later, specialist uses of the same picture: the one who watches.

In science在科學裡，a sentinel species是一種 sentinel species（指標物種） is an animal whose trouble warns us that the place is sick是指某種動物出狀況就警告我們這地方生病了；in medicine在醫學裡 a sentinel node是第一個哨兵淋巴結（sentinel node） is the first lymph node doctors check是醫生會先檢查的第一個淋巴結。Those are later, specialist uses of the same picture這些都是後來從同一個畫面延伸出的專業用法：the one who watches也就是「負責看守的那個」。

There is also a rare verb, to sentinel, meaning to watch over, but the noun is what you will meet. Though actually, the job is simple: stay awake, notice, call out.

There is also a rare verb還有一個少見的動詞，to sentinel也是 sentinel，meaning to watch over意思是看守著，but the noun is what you will meet但你會遇到的是名詞用法。Though actually不過其實，the job is simple這件工作很單純：stay awake保持清醒，notice留意，call out發出警告。