Etymology From French effectif, from Latin effectīvus (“productive; effective”), from efficiō (“to make; to bring about”), equivalent to effect + -ive.
Having the power to produce a required effect or effects.
The pill is an effective method of birth control.
"Capital idea; we'll go together and complain: two will be more effective," suggested Mr. Belting.1923, Ernest Bramah [pseudonym; Ernest Brammah Smith], “(please specify the page)”, in The Eyes of Max Carrados, London: Grant Richards, →OCLC:
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Fire ants circumvented the problem of an ineffective sting by having an unusual and highly effective venom that when daubed or sprayed on other ants penetrates their waxy protective integumental barrier and kills or disables them.2016, Justin O. Schmidt, The Sting of the Wild, Johns Hopkins University Press, →ISBN, page 102:
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Producing a decided or decisive effect.
The president delivered an effective speech!
Whosoever is an effective, real cause of doing his neighbour wrong, is criminal.1651, Jer[emy] Taylor, The Rule and Exercises of Holy Living. […], 2nd edition, London: […] Francis Ashe […], →OCLC:
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Efficient, serviceable, or operative, available for useful work.
How long does it take to make a bunch of civilians an effective military force?
My effective income after taxes and child support is $500 a month.
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The effective radiated power is determined by multiplying the transmitter power output with the antenna gain.
The effective voltage of an alternating current is 0.7 times its peak voltage.
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Actually in effect.
effective immediately
The curfew is effective at midnight.
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Geometry, Mathematics, SciencesOf a cycle or divisor Having no negative coefficients.
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Algebra, Mathematics, SciencesOf a group action Such that no group element acts trivially.
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Natural sciences, Physical sciences, PhysicsFor any effective theory approximate; Not describing the fundamental dynamic changes in some system as they happen.
Etymology From French effectif, from Latin effectīvus (“productive; effective”), from efficiō (“to make; to bring about”), equivalent to effect + -ive.
The Army of the West reached Corinth sometime after the battle of Shiloh. We were 15,000 effectives, and brought Beauregard's effective force up to 45,000 men.1876, Dabney Herndon Maury; Southern Historical Society Papers: Volume 2, Number 4, Recollections of the Elkhorn Campaign: