警惕 (jǐng tì): 경계하다

When traveling abroad, the tour guide reminded us to be on the alert for pickpockets, especially in crowded places.

The doctor warned him that if he continued to smoke and drink, he should be on the alert for serious illnesses.

When shopping online, consumers should be on the alert for goods with absurdly low prices to avoid being cheated.

The teacher reminded the students to be on the alert against excessive nervousness before an exam, so as not to affect their normal performance.

Recently, several thefts occurred in the neighborhood, so residents began to be on the alert and would check whether the doors and windows were locked at night.