1The reason, cause, or circumstances for an event or decision; often used in documents and formal notices.
退職の事由を明記してください。
Please state the reason for your resignation.
病欠の事由を証明する診断書を提出した。
He submitted a medical certificate proving the reason for his sick leave.
その決定の事由は明確に説明されなかった。
The reasons for that decision were not clearly explained.