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to be effective; to take effect; to work (medicine); to be good (for)
to work; to function well
to be possible (to do, use, etc.); to be able to
to taste (alcohol); to try
この薬は頭痛によく効く。
This medicine works well for headaches.
ブレーキがしっかり効いて安全に止まれた。
The brakes worked well, and I was able to stop safely.
漢方薬は風邪に効くと言われている。
Herbal medicine is said to be effective for colds.