異変

1. Origins, structure, and basic meaning

• Structure: 異変 is read as いへん and is a noun for an abnormal change, unusual sign, or event that departs from the ordinary state.
• Basic usage: Use 異変を感じる when someone senses a problem and 異変が生じる when the abnormal change itself occurs.

2. Common pitfalls and similar expressions

• Sensing and occurring
  • 異変を感じる centers the observer, whereas 異変が生じる states that a change has arisen.
• No fixed scale
  • Because one can say 小さな異変, the word does not necessarily refer only to a major incident.