Dictionary.com

efficacious

[ ef-i-key-shuhs ]
/ ˌɛf ɪˈkeɪ ʃəs /
Save This Word!
See synonyms for: efficacious / efficaciously / efficaciousness on Thesaurus.com

adjective
capable of having the desired result or effect; effective as a means, measure, remedy, etc.: The medicine is efficacious in stopping a cough.
QUIZ
WILL YOU SAIL OR STUMBLE ON THESE GRAMMAR QUESTIONS?
Smoothly step over to these common grammar mistakes that trip many people up. Good luck!
Question 1 of 7
Fill in the blank: I can’t figure out _____ gave me this gift.

Origin of efficacious

First recorded in 1520–30; from Latin efficāci- (stem of efficax ) “effectual.” See efficient, -acious

OTHER WORDS FROM efficacious

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use efficacious in a sentence

British Dictionary definitions for efficacious

efficacious
/ (ˌɛfɪˈkeɪʃəs) /

adjective
capable of or successful in producing an intended result; effective as a means, remedy, etc

Derived forms of efficacious

efficaciously, adverbefficaciousness, noun

Word Origin for efficacious

C16: from Latin efficāx powerful, efficient, from efficere to achieve; see effect
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
FEEDBACK