平安 (píng ān) means 'safe and sound' as well as 'peaceful, at peace' — it covers both physical safety and a state of calm. 安全 (ān quán) focuses strictly on being free from danger or harm, while 安宁 (ān níng) emphasizes tranquility and absence of disturbance, often for places or one's mind. 平安 is common in well-wishes like 一路平安 (have a safe trip).