/ˌrɛtrəˈæktɪv/ – adjective
Definition: có hiệu lực trở về trước, có hiệu lực hồi tố.
A more thorough explanation: “Retroactive” refers to a law, rule, or decision that applies to past events or actions, affecting them as if it had been in place at the time they occurred.
Example: The new tax law was made retroactive to January 1st of this year, meaning that the changes will apply to income earned earlier in the year.