Part of speech: Adjective (satellite)
producing no result or effect
Example: a futile effort; the therapy was ineffectual; an otiose undertaking; an unavailing attempt
Ineffectual, Futile, Unavailing, Otiose
un – A related word in the same word family.
availing – A related word in the same word family.
Related words show how one ancient root could spawn dozens of modern meanings.