The kanji 沸 means "to boil," "to bubble," "to seethe," or "to become excited." It conveys the idea of a liquid changing state due to heat, or figuratively, a strong emotional reaction. It implies a rapid and often visible change or agitation.

・On-yomi (音読み): フツ (futsu) ・Kun-yomi (訓読み): わ(く) (wa(ku))

⚫︎ お湯が沸騰する。 Translation: The water boils. ⚫︎ 怒りで心が沸き返る。 Translation: My heart boils with anger. ⚫︎ 会場が熱気に沸いた。 Translation: The venue was filled with excitement.

The kanji 沸 is a phono-semantic compound (形声文字, けいせいもじ). The semantic component is 水 (みず, water), which suggests the presence of water or liquid. The phonetic component is 弗 (ふつ, futsu), which has a similar sound and suggests the action of something bubbling or agitating. The combination of these two components forms the meaning of "boiling" or "bubbling."