遡及

1. Origins, structure, and basic meaning

• Structure: 遡及 is read as そきゅう and is a noun and する verb for retroactive application, extending a rule or system back to an earlier time or event.
• Basic usage: The issue appears in 規則の遡及, while the reach into the past appears in 過去に遡及させる.

2. Common pitfalls and similar expressions

• Direction of effect
  • It is mainly used in formal or abstract contexts where a newly set rule affects earlier events.
• Difference from 遡る
  • 遡る broadly means tracing back through time, a route, or an origin; 遡及 focuses on applying an effect or judgment retroactively.