efficacious

What does “efficacious” mean?

adjective.successful in producing a desired or intended result; effective.

SAT Usage

this term is often found in passages related to science, medicine, or social sciences, where it describes methods, treatments, or policies that achieve intended outcomes. It emphasizes not just effectiveness, but also a reliable and proven capability to produce results, distinguishing it from terms like "efficient," which focuses more on resource use rather than result success.

Common Confusions

Efficacious implies a proven ability to produce desired results, while efficient usually suggests a focus on minimizing resources or time rather than ensuring successful outcomes.

Example Sentences

• The new drug proved highly efficacious in clinical trials.

Word Parts: How to Remember “efficacious”

Break “efficacious” into its parts: ex- (out of, from) + -fac- (make, do). Knowing roots like these helps you decode unfamiliar SAT vocabulary.

• Prefix: ex- out of, from (Latin)
• Root: -fac- make, do (Latin)