effectual

• effectuall (obsolete)

From Middle English effectual, effectuel, from Old French effectuel, from Late Latin effectualis.

• IPA^(key): /iˈfɛkt͡ʃuəl/

effectual (comparative more effectual, superlative most effectual)

1. Producing the intended result; entirely adequate.
   • 1749, [John Cleland], “(Please specify the letter or volume)”, in Memoirs of a Woman of Pleasure [Fanny Hill], London: […] G. Fenton [i.e., Fenton and Ralph Griffiths] […], →OCLC:

     Redoubling, then, the active energy of his thrusts, favoured by the fervid appetite of my motions, the soft oiled wards can no longer stand so effectual a picklock, but yield, and open him an entrance.

   • 1822, John Barclay, chapter I, in An Inquiry Into the Opinions, Ancient and Modern, Concerning Life and Organization‎, Edinburgh, London: Bell & Bradfute; Waugh & Innes; G. & W. B. Whittaker, section I, page 1:

     In the living state, the body is observed to […] adopt most effectual measures for the permanent continuance of its species.

• ineffectual