Peril is serious danger or risk, the kind that could lead to real harm or disaster. When mountain climbers face the perils of avalanches and sudden storms, they're confronting genuine threats to their safety. When a ship captain warns of peril at sea, he means the crew faces actual danger that could result in injury, death, or the loss of the ship.

The word carries weight because it describes danger that matters. You wouldn't say your homework assignment puts you in peril, but you might read about explorers who ventured into unknown territories at great peril to themselves. A knight in a medieval tale might rescue someone from peril, meaning from serious, immediate danger.

Perilous is the adjective form: a perilous journey is one filled with real hazards and uncertain outcomes. When historians write about perilous times, they mean periods when people faced genuine threats to their way of life or safety. The word suggests both the reality of danger and the courage required to face it.