capable of having the desired result or effect; effective as a means, measure, remedy, etc.: The medicine is efficacious in stopping a cough.
Origin of efficacious
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
capable of or successful in producing an intended result; effective as a means, remedy, etc
Word Origin for efficacious
C16: from Latin efficāx powerful, efficient, from efficere to achieve; see effect
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