Efficacy

medium

EF-ih-kuh-see

noun

Definition

the power to produce a desired effect or result; effectiveness

Examples

Clinical trials questioned the efficacy of the new vaccine in older patients.
The efficacy of the policy will only become clear over several years.

Synonyms

effectivenesspotencyefficiencyproductiveness

Antonyms

ineffectivenessfutilityimpotenceinefficacy

Categories

GRE Tip

Efficacy is a medium-difficulty GRE word. On the GRE, you might see it paired with synonyms like "effectiveness" or "potency" in Sentence Equivalence questions. Look for contrast clues (however, despite, although) that signal the opposite meaning. Words like "ineffectiveness".

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