a.

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

   紗窗能有效地擋住蚊子。

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.

   國會通過的法案一經總統簽署立即生效。

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

   那樣使用顏色效果甚佳。

4. 實際的，事實上的[Z]
   Although there is a parliament, the army is in effective control of the country.

   雖然有議會存在，但軍隊實際上控制著這個國家。

5. 有戰鬥力的[Z]

n.

1. 實際可作戰的部隊（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.