effectiveness [effectivenesses](capacity or potential) noun [UK: ɪ.ˈfekt.ɪv.nəs] [US: ɪ.ˈfekt.ɪv.nəs]Don't doubt the effectiveness of this drug. = No dude de la eficacia de este medicamento.
efficacy [efficacies](ability to produce effect) noun [UK: ˈe.fɪk.ə.si] [US: ˈe.fɪˌk.æ.si]Don't confuse efficacy with efficiency. = No confundas eficacia con eficiencia.
ineficacianoun {f}
ineffectiveness(condition of being ineffective) noun [UK: ˌɪ.nɪ.ˈfek.tɪv.nəs] [US: ˌɪ.nə.ˈfek.tɪv.nəs]