effective/əˋfɛktIv; IˈfektIv/adj 1 having the result that you want [ ineffective ] 有效的﹔产生预期效果的: an effective way to teach reading 一种教授阅读的有效方法a highly effective method 一种非常有效的方法2 [not before noun 不用于名词前] if a law, agreement, or system becomes effective, it officially starts〔法律﹑协议或制度〕生效的: +from The new regulations are effective from April 5th. 新规则从 4 月 5 日起生效。—effectiveness n [U] COST EFFECTIVE