D defs.my
Entry 1 sense Webster, 1913

Efficacious

/ĕfˌ-ək-āsh'-əs/ · Ef·fi·ca·cious · IPA /ˌɛf.əˈkeɪ.ʃəs/
01 a. Possessing the quality of being effective; productive of, or powerful to produce, the effect intended; as, an efficacious law.
  1. 1.
    Possessing the quality of being effective; productive of, or powerful to produce, the effect intended; as, an efficacious law.
Syn. See Effectual.