a.

1. 有效的[（+against/in）][+to-v]
   Window screens are effective in keeping out mosquitoes.

   纱窗能有效地挡住蚊子。

2. （法律等）生效的，起作用的[Z]
   A bill passed by congress becomes effective as soon as the President signs it.

   国会通过的法案一经总统签署立即生效。

3. 给人深刻印象的，有力的
   That's rather an effective use of color.

   那样使用颜色效果甚佳。

4. 实际的，事实上的[Z]
   Although there is a parliament, the army is in effective control of the country.

   虽然有议会存在，但军队实际上控制着这个国家。

5. 有战斗力的[Z]

n.

1. 实际可作战的部队（或士兵）[P]

adj.

1. producing a desired or intended result.
2. (of a law or policy) operative.
3. existing in fact, though not formally acknowledged as such.

n.