noun
speedy effect; quick results; immediate action
Often used for medicines, treatments, or measures that take effect quickly. Contrasts with 遅効 (delayed effect).
See also: 遅効
この薬は速効があるので、すぐに痛みが治まります。
This medicine has a speedy effect, so the pain will subside quickly.
速効性の肥料を使うと、植物
Using a quick-acting fertilizer will quickly revive the plants.