急行
きゅうこう · kyuukou · JLPT N4 · noun
bus
🚆 急行 = hurry (急) + go (行): the train that goes in a hurry
急 means urgent or hurried, as in 急ぐ (isogu, to hurry). 行 means to go, as in 行く (iku). A hurry-go service skips minor stops, so 急行 is the express train or bus. Sound hook: kyuukou starts like a cue to go.
急 — heart radical 心 + 及 (reach)
A semantic-phonetic compound: the heart radical 心 supplies the meaning (an emotional state) while 及 ('to reach, catch up') gives the sound. Originally it depicted a racing, anxious heart — hence the modern senses 'urgent,' 'hurried,' and 'impatient.'
行 — crossroads pictograph (left 彳 + right 亍)
行 originally pictured a four-way crossroads in oracle bone script, with two paths meeting. From 'road' it extended to 'walk, go, travel,' and then to 'a row, line' or 'business firm' (read háng). The two halves 彳 and 亍 are the split sides of that ancient crossroads.