/ˌrɛtrəʊˈæktɪvɪti/ – Noun
Definition: hiệu lực trở về trước, hiệu lực hồi tố.
A more thorough explanation: Retroactivity refers to the application of a law, regulation, or decision to events that occurred before the law was enacted or before the decision was made. It means that the law or decision has an effect on past actions or events.
Example: The new tax law was applied with retroactivity to January 1st of the current year, impacting all financial transactions made since the beginning of the year.