• 危険きけん — danger
• 危機きき — crisis
• 危あぶない — dangerous
• 危あやうい — precarious; at risk
• 危害きがい — harm; injury
• 危機感ききかん — sense of danger; urgency

The character 危 originally depicted a person on a high, unstable structure — representing danger or instability. It’s common in signage and safety instructions and is closely associated with cautionary contexts.

この場所ばしょは 危険きけんです。
This place is dangerous.

橋はしを 渡わたるのは 危あぶないので 気きをつけてください。
Crossing the bridge is dangerous, so please be careful.