KEY: Auxiliary.
SYN: Helpful, abetting, aiding, accessory, promotive, conducive, assistant, ancillary, assisting, subsidiary, helping.
ANT: Unassisting, unconducive, unpromotive, redundant, superfluous, obstructive, retardative, irrelevant, cumbersome.
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KEY: Avail \v.\
SYN: Suffice, hold, stand, endure, answer, tell, profit, help, benefit, advantage, service, use, utility.
ANT: Fail, fall, disappoint, betray.
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KEY: Avail.
SYN: Profit, help, benefit, advantage, use, utility, service.