effective强调产生实际效果的能力,无比较级和最高级。

用作定语
▲～+n.
 These are effective measures.这些都是有效的措施。
The medicine is an effective cure for a headache.这药治头痛疗效很好。
Her brother is the king, but she is the effective ruler.她的兄弟是国王,但她才是实际的主宰者。
The book has a very effective closing chapter.这本书的结尾一章给人印象极深。
用作表语
▲S+be+～
 The law became effective last month.这条法律于上个月生效。
That display is very effective.那个展览使人赏心悦目。
▲S+be+～+prep.-phrase
 The medicine is effective against cancer.这药物治癌有效。
The clothes are effective in keeping cool in warm weather.热天穿淡色衣服使人凉爽。

effective, effectual, efficacious, efficient
这四个形容词都有“(能够)生效”的含意。effective强调效用,意为“有效的”,可用于人或事物; effectual强调效果,意为“(最终)奏效的”,一般不用于人; efficacious强调效验,意为“灵验的”,不用于人,多表示药物和治疗的效果; efficient强调功效,意为“有成效的,效率高的”,可用于人或事,指人表示“能干的”,指方法、机器表示“收效大的”。

［同义词］   efficient, capable, impressive
［反义词］   ineffective, incompetent, useless