How to say "fermentation" in Japanese

• 発酵はっこうCommon
  noun, suru verb, intransitive verbThe word you want for fermentation as an actual chemical or biological process, such as in brewing or baking; the gloss 'zymosis' points to the same literal, technical sense.
  イーストはビールを発酵はっこうさせる。↗

  Yeast makes beer ferment.
• 沸騰ふっとうJLPT N1approx.Common
  noun, suru verb, intransitive verbNot the word for the biochemical process: its 'fermentation' is the figurative English 'ferment'—turmoil or heated excitement, e.g. of a debate—rather than any literal process.
  国内こくないは防衛ぼうえい問題もんだいで沸騰ふっとうした。↗

  The country seethed over the issue of national defense.

Choose 発酵 for fermentation as a literal chemical or biological process, as in brewing or baking; 沸騰 matches only the figurative English 'ferment'—heated excitement or agitation—not the process itself.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 発酵はっこうfermentation
• 沸騰ふっとうbecoming heated (e.g. of a debate)