effective
Working well and producing the result you want.
Effective means producing the result you want or need. When something is effective, it works well and gets the job done. An effective study method helps you actually learn and remember the material. An effective medicine makes sick people better. An effective speech persuades listeners to see things your way.
The word focuses on results, not effort. You might spend hours on a science project, but if it doesn't clearly demonstrate what you were trying to show, it isn't effective. A basketball player who takes many shots but rarely scores isn't playing effectively. On the other hand, a simple solution that solves a problem completely is highly effective, even if it seems easy.
Notice how effective differs from efficient. Something efficient gets results without wasting time or resources: it's fast and economical. Something effective gets results, regardless of how long it takes. A thorough, time-consuming plan can be both effective (it works) and inefficient (it takes forever). The best solutions are usually both effective and efficient, but if you have to choose between them, effective matters more. After all, the fastest way to do something is worthless if it doesn't actually work.