急
きゅう · kyuu · JLPT N4 · na-adj
urgent
🚑 kyuu sounds like cue: on cue you must rush, no time to wait
急 is built from a grasping hand over 心 (heart): a heart seized by haste. That one idea covers all three senses: an urgent matter, a sudden change, a steep slope that rushes upward. Seen in 急行 (express train) and 救急 (first aid).
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.'