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English definition of “retroactive”

retroactive

adjective     /ˌret.rəʊˈæk.tɪv/ US  /-roʊ-/ (also retrospective) formal
If a law or decision, etc. is retroactive, it has effect from a date before it was approved: the first British law to have retroactive effectRelating to timeRules and laws retroactively     /-li/ adverb Relating to time
(Definition of retroactive adjective from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)
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