1. 有效的;能产生预期效果的
    Something that is effective works well and produces the results that were intended.

    e.g. The project looks at how we could be more effective in encouraging students to enter teacher training...
           该项目着眼于我们如何能够更加有效地鼓励学生参与教师培训。
    e.g. Simple antibiotics are effective against this organism...
           一般的抗生素能够有效对抗这种微生物。

2. 实际的;事实上的
    Effective means having a particular role or result in practice, though not officially or in theory.

    e.g. They have had effective control of the area since the security forces left.
           自从安全部队撤离后，他们实际上控制了该地区。
    e.g. ...a restructuring that would have resulted in an effective increase on one of their most popular excursion fares.
           原本会使他们最热门的一条短途旅游线路的费用出现实质性上涨的调整

3. （法律、协议等）生效的，起作用的
    When something such as a law or an agreement becomes effective, it begins officially to apply or be valid.

    e.g. The new rules will become effective in the next few days.
           新规定将在几天后生效。