warn

1. Origins, structure, and basic meaning

• Structure: The on reading is けい, and no kun reading is listed. It has 19 strokes and relates to cautioning against and announcing danger.
• Basic usage: 警告 is read けいこく, and 警報 is read けいほう.

2. Common pitfalls and similar expressions

• 警告 / 警報
  • 警告 means warning. It is a noun read けいこく. It is a direct warning or act of cautioning someone about danger or a problem.
  • 画面に容量不足の警告が表示された。 means “A warning that there was not enough capacity appeared on the screen.”
  • 警報 means alarm or warning. It is a noun read けいほう. It is an alert that is issued or sounded to announce danger.
  • 警報が出たため、急いで川から離れました。 means “An alarm was issued, so we quickly moved away from the river.”