既往

1. Origins, structure, and basic meaning

• Structure: 既往 is read as きおう and is a formal noun meaning something past or previous, often used in compounds for medical history or earlier investigations.
• Basic usage: Referring to the medical-history field on a questionnaire appears in 問診票の既往歴, while formally modifying earlier survey results appears in 既往の調査結果.

2. Common pitfalls and similar expressions

• Difference from 過去
  • 既往 readily appears in medical records or reports rather than ordinary reference to the past.