Retroactive (adjective)

1. Having effect on or relating to a time before a law, rule, or decision was made or implemented.
2. Having an effect on something that happened in the past.

Origin:

From the latin word "retro" meaning "back" and "actus" meaning "act" or "performing".

Examples:

1. The new law was made retroactive, which means it applies to crimes that were committed before it was passed.
2. The company's decision to change the retirement plan was retroactive and affected the employees who had already retired.
3. The court's ruling was retroactive, which means it applied to the cases that had already been decided.
4. The tax cut was made retroactive, which means it applies to the tax year that has already ended.
5. The new policy was made retroactive, which means it applies to the employees who have already been hired.