Date: 14th century
a. producing a decided, decisive, or desired effect <an effective policy> b. impressive, striking <a gold lamé fabric studded with effective…precious stones — Stanley Marcus> 2. ready for service or action <effective manpower> 3. actual <the need to increase effective demand for goods> 4. being in effect ; operative <the tax becomes effective next year> 5. of a rate of interest equal to the rate of simple interest that yields the same amount when the interest is paid once at the end of the interest period as a quoted rate of interest does when calculated at compound interest over the same period — compare nominal 4 • effectiveness noun • effectivity noun Synonyms: effective, effectual, efficient, efficacious mean producing or capable of producing a result. effective stresses the actual production of or the power to produce an effect <an effective rebuttal>. effectual suggests the accomplishment of a desired result especially as viewed after the fact <the measures to stop the pilfering proved effectual>. efficient suggests an acting or a potential for action or use in such a way as to avoid loss or waste of energy in effecting, producing, or functioning <an efficient small car>. efficacious suggests possession of a special quality or virtue that gives effective power <a detergent that is efficacious in removing grease>. II. noun Date: 1722 one that is effective; especially a soldier equipped for duty
New Collegiate Dictionary. 2001.