effective

Universal Words adjective 1 producing the result that is wanted or intended; producing a successful result: Long prison sentences can be a very effective deterrent for offenders. * Aspirin is a simple but highly effective treatment. * drugs that are effective against cancer * Some people believe that violence is an effective way of protesting. * I admire the effective use of colour in her paintings. OPPINEFFECTIVE seealsoCOST-EFFECTIVE 2 [onlybeforenoun] in reality, although not officially intended: the effective, if not the actual, leader of the party * In spite of what they are told, parents have no effective choice of schools. * He has now taken effective control of the country. 3 (formal) (of laws and rules) coming into use: The new speed limit on this road becomes effective from 1 June. effectiveness (also less frequent effectivity ) noun [U]: to check the effectiveness of the security system