rápido
/ˈrapido/ · A1 · adv
rapidly, quickly, fast
🚄 rápido = rapid + o: same Latin root, rapidus, as English rapid
From Latin rapidus (swift, seizing), from rapere, to snatch. English rapid is the same word, so just add -o. It also names a river rapid and an express train, both the fast version of the thing. Stress falls on RÁ.