SYN: Hinder, obstruct, bar, neutralize, nullify, thwart, intercept, anticipate, forefend, frustrate, obviate, checkmate.
ANT: Promote, aid, facilitate, expedite, encourage, advance, accelerate, induce, cause, produce.
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KEY: Prevention.
SYN: Obstruction, stoppage, interruption, hinderance.
ANT: Help, aid, succor, acceleration.
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KEY: Previous.
SYN: Antecedent, prior, preceding, anterior, foregoing, former, earlier.
ANT: Subsequent, posterior, succeeding, following, later.