Inefficacious

ˌɪnɪˈfɪkeɪʃəs

adjective

not producing the desired effect; ineffective

The word 'inefficacious' comes from the Latin word 'inefficax', which means 'not producing the desired effect'. It is often used to describe something that is not successful or does not achieve its intended purpose.

Bayta joined the three girls who were taking turns at the eternally applied and eternally inefficacious remedies of shoulder-patting, hair-smoothing, and incoherent murmuring.

Asimov, Isaac

Foundation 2 - Foundation and Empire