沸 seethe, boil, ferment, uproar, breed 8 strokes jōyō, taught in secondary school old JLPT 2 #1709 in newspapers Readings Onフツ Kunわ.く、わ.かす In Chinese 沸 Words written with it 沸かす わかす to boil N4 沸く わく to grow hot (e.g. water) N4 沸騰 ふっとう boiling N1 沸き起こる わきおこる to well up 湯沸かし器 ゆわかしき water heater 沸き返る わきかえる to boil up