The kanji character 急 primarily conveys the idea of "urgent," "sudden," or "hasty." It implies a state of being pressed for time, requiring immediate action, or occurring unexpectedly. It can also describe a quick change or a rapid increase in something.

・On-yomi (音読み): キュウ (kyū) ・Kun-yomi (訓読み): いそ（ぐ） (iso(gu))

⚫︎ 急に雨が降り出した。 Translation: It started raining suddenly. ⚫︎ 急行電車 Translation: Express train (rapid train). ⚫︎ 緊急事態 Translation: Emergency situation.

The kanji 急 is a phono-semantic compound (形声文字, keisei moji). The left side is the radical 心 (kokoro, heart/mind), and the right side is 及 (oyobu, to reach).. The original meaning was related to a person's emotions. It represents a state of the heart that is hurried and anxious, the heart that "reaches out" or "is in a hurry". Over time, it broadened to represent the general idea of urgency and suddenness.