Efficacious

//ˌɛf.ɪˈkeɪ.ʃəs// adj

adj ·Moderate ·College level

Definitions

Adjective
  1. 1
    Effective; possessing efficacy. formal

    "This medicine is efficacious."

Adjective
  1. 1
    producing or capable of producing an intended result or having a striking effect wordnet
  2. 2
    marked by qualities giving the power to produce an intended effect wordnet

Synonyms

All synonyms
effectiveableactiveadequateauthoritativebeneficial

Example

More examples

"Goldman Sachs, the American financial powerhouse, is trying to factor into its investment decisions and counsel all possible Omicron outcomes — from a worst-case scenario of greater virulence and vaccine-evasion to the nice surprise that the vaccines remain efficacious, and Omicron turns out to be more benign than its forerunner."

Etymology

From Old French efficacieux, from Latin efficāx (“efficacious”) + -ous, from efficere (“to effect, to accomplish”); see effect.

More for "efficacious"

SynonymsSentencesPronunciationTranslate

Next best steps

Find stronger synonymsSee usage examplesCheck pronunciationBrowse writing guides

Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.