Definition

Able to produce the result that is wanted or intended.

Example

The new medicine proved to be efficacious in treating the disease.

Conversation

I heard that new herbal tea is really efficacious for stress relief.

Oh really? I could use something like that after this week!

Yeah, I read some reviews, and people seem to love how it works.

Sounds like I should definitely give it a try!

Synonyms & Antonyms

Root Explanation

Efficacious → It is formed from "efficax" (meaning effective) and the suffix "-ous" (meaning full of). The word "efficacious" means full of effectiveness or capable of producing a desired effect.

Memory Tip

Think of something that is 'full of effectiveness' — 'efficax' means effective, and '-ous' means full of.

Visually Confused Words