efficacy [efficacies](ability to produce effect) noun [UK: ˈe.fɪk.ə.si] [US: ˈe.fɪˌk.æ.si]Don't confuse efficacy with efficiency. = Non confondere efficacia con rendimento.
strength [strengths](intensity of a force or power) noun [UK: streŋθ] [US: ˈstreŋkθ]
inefficacianoun {f}
inefficacy(the condition of being ineffective) noun [UK: ɪnˈefɪkəsi] [US: ɪnˈefɪkəsi]