效力的英文：
serve
potence
force
efficacy

potent liquor;a potent toxin.
有效力的酒;有效力的毒素

Time works wonders.
时间可以创造奇迹或时间的效力不可思议。

feeling of efficacy
效力感

The law should remain in force.
法律应当有效力。

The medicine is efficacious
这药很有效力。

a retrospective pay rise
有追溯效力的加薪.

an ex post facto law
有追溯效力的法律

Efficiency will be multiplied several times.
效力将提高好几倍。

The legislation was made retrospective.
该项法规具有追溯效力。

The patriot rendered services to his country all his life.
爱国者毕生为国家效力。

to serve the landlord
为地主干活

Persons serving on the Appellate Body shall serve in rotation.
上诉机构人员任职应实行轮换。

They drafted him to serve as their delegate.
他们选派他作他们的代表。

All their songs have a lingering potency.
他们所有的歌曲都有挥之不去的影响力。

They testify to the extraordinary potency of his personality.
这些事情证明了他非凡的人格魅力。

The drug will lose its potency when exposed to moisture.
这药一受潮就会失效。

by (main) force
用蛮力, 全靠气力; 以最大的力气

The force is spectacular!
这个瀑布很壮观！

resultant force
合力