inefficacious
Failing to work
Inefficacious means not producing the desired effect—a formal way of saying something doesn't work.
The word typically describes remedies, treatments, or measures that fail to achieve their purpose: The vaccine proved inefficacious against the new variant.
It's the opposite of efficacious and carries a more technical or clinical tone than simply saying ineffective.
Incapable of producing results
- vainExcessively proud or futile
- fruitlessProducing no useful outcome
- pointlessLacking any purpose
- uselessWithout practical value
unavailing · bootless · nugatory · abortive · idle · empty · hollow · unproductive
Lacking power or efficacy
- powerlessLacking strength or authority
- helplessUnable to act independently
- weakLacking power or force
- feebleWeak and ineffective
enfeebled · incapable · inadequate · insufficient · lacking · inept · incompetent · debilitated
Not achieving desired outcome
- failingFlaw in one's nature
- inoperativeNot able to function
- nonfunctionalNot performing its purpose
- brokenDamaged beyond function
defunct · malfunctioning · dysfunctional · flawed · faulty · defective · unworkable · impractical
futile
Incapable of producing results
useless · unavailing · bootless · nugatory · abortive · idle · empty · hollow · unproductive · unprofitable
impotent
Lacking power or efficacy
feeble · enfeebled · incapable · inadequate · insufficient · lacking · inept · incompetent · debilitated · enervated
unsuccessful
Not achieving desired outcome
- failingFlaw in one's nature
- inoperativeNot able to function
- nonfunctionalNot performing its purpose
broken · defunct · malfunctioning · dysfunctional · flawed · faulty · defective · unworkable · impractical · unreliable
inefficaciousefficacious
Producing intended effects
effective · effectual · successful · productive · useful
effect, effective, efficiency, efficient, sufficient, proficient, deficiency, inefficient, proficiency