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efficacious Syllabification: ef·fi·ca·cious
Pronunciation: /ˌefəˈkāSHəs/

Definition of efficacious in English:


(Typically of something inanimate or abstract) successful in producing a desired or intended result; effective: the vaccine has proved both efficacious and safe
More example sentences
  • During this era, biological discovery is accelerating, resulting in the development of safer and more efficacious drugs.
  • It may not mean that the ultimate result is not efficacious.
  • Both drugs were equally efficacious in improving auditory hallucinations and suspiciousness.


Pronunciation: /ˌefəˈkāSHəslē/
Example sentences
  • The efforts were directed at acquainting students with HIV and risk, encouraging them to assess their individual risk, and then teaching them how to efficaciously reduce or avoid that risk.
  • The police may permit individuals to donate DNA samples at their local laboratory, thereby maximizing compliance and assuring that the procedures are conducted safely and efficaciously.
  • Some of these interpretations suggest that the new laws may not efficaciously exclude appeals based on natural justice.
Pronunciation: /ˌefəˈkāSHəsnəs/
Example sentences
  • Where he differs is in his claims about power and its alleged efficaciousness in bringing about ‘knowledge’.
  • Obviously some weapon systems are more effective than others, but the efficaciousness of air defence measures depend basically on the gap between the technological/industrial investment and output of the competing sides.
  • Stating that the first big downpour is usually a test to check the efficaciousness of the drainage system, he said it had helped the department to gauge the problem areas in the city.


Early 16th century: from Latin efficax, efficac- (from efficere 'accomplish': see effect) + -ious.

Words that rhyme with efficacious

Athanasius, audacious, bodacious, cactaceous, capacious, carbonaceous, contumacious, Cretaceous, curvaceous, disputatious, edacious, fallacious, farinaceous, flirtatious, foliaceous, fugacious, gracious, hellacious, herbaceous, Ignatius, loquacious, mendacious, mordacious, ostentatious, perspicacious, pertinacious, pugnacious, rapacious, sagacious, salacious, saponaceous, sebaceous, sequacious, setaceous, spacious, tenacious, veracious, vexatious, vivacious, voracious
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