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English definition of “fast”

fast

adverb     /fɑːst/ US  /fæst/
A2 quickly : The accident was caused by people driving too fast in bad conditions . You'll have to act fast. Children's publishing is a fast-growing business .Fast and rapidShort in time Grammar:Fast, quick or quickly?Fast and quick mean moving with great speed. Fast is both an adjective and an adverb. Quick is an adjective and the adverb form is quickly.
(Definition of fast adverb from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)
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