急

sudden; hurry; emergency; steep

9 strokes. Taught in grade 3. Newspaper frequency rank 309.

Readings

キュウ (on reading): 急 (きゅう) sudden; 急速 (きゅうそく) rapid (e.g. progress)
いそぐ (kun reading): 急ぐ (いそぐ) to hurry; 生き急ぐ (いきいそぐ) to live fast (and recklessly)
いそぎ (kun reading): 急ぎ (いそぎ) haste; 取り急ぎ (とりいそぎ) in haste
せく (kun reading): 急かす (せかす) to hurry (up); 急く (せく) to hurry

急 (きゅう) sudden
急速 (きゅうそく) rapid (e.g. progress)
特急 (とっきゅう) limited express (train for which a limited-express ticket is required)
緊急 (きんきゅう) urgency
急激 (きゅうげき) sudden
急ぐ (いそぐ) to hurry
生き急ぐ (いきいそぐ) to live fast (and recklessly)
善は急げ (ぜんはいそげ) move with haste (when you have no doubts)
取り急ぐ (とりいそぐ) to hurry
急いで (いそいで) hurriedly
急ぎ (いそぎ) haste
取り急ぎ (とりいそぎ) in haste
大急ぎ (おおいそぎ) great hurry
急ぎ足 (いそぎあし) fast pace
買い急ぎ (かいいそぎ) buying spree
急かす (せかす) to hurry (up)
急く (せく) to hurry
急きたてられる (せきたてられる) to be hurried
急かせる (せかせる) to hurry (up)
急いては事を仕損ずる (せいてはことをしそんずる) haste makes waste

329 words in all.