N4 - 急行きゅうこう
speedy, express
N4 - 特急とっきゅう
limited express train (faster than an express train)
N3 - 急激きゅうげき
sudden, precipitous, radical
N3 - 急速きゅうそく
rapid (e.g. progress)
N2 - 至急しきゅう
urgent, pressing
N1 - 緊急きんきゅう
urgent, pressing, emergency
N1 - 準急じゅんきゅう
local express (train slower than an express)
N1 - 急かすせかす
to hurry, to urge on