retroactive

The adjective retroactive refers to something happening now that affects the past. For example, a retroactive tax is one that is passed at one time, but payable back to a time before the tax was passed.

The Latin word retroagere, an ancestor of the adjective retroactive, means "drive or turn back," and goes along with the meaning of the word. Sometimes governments pass rulings that are set as if they were in effect before the ruling was even made, and that means they are retroactive. On the bright side, you might be awarded a salary raise that is retroactive, meaning you'll get paid more for work you did in the past. And, retroactive fads in clothing keep vintage clothing stores in business.

Definitions of retroactive
1

adj affecting things past

retroactive tax increase”
Synonyms:
ex post facto, retro
retrospective
concerned with or related to the past

adj descriptive of any event or stimulus or process that has an effect on the effects of events or stimuli or process that occurred previously

Antonyms:
proactive
descriptive of any event or stimulus or process that has an effect on events or stimuli or processes that occur subsequently

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