How to say "rot" in Japanese

• くさるJLPT N3approx.Common
  godan verb, intransitive verbThe verb for the process of rotting: food going bad or spoiling, and organic matter decaying. This is the word you want when you say that something rots or has gone bad.
  これらのオレンジは腐くさっている。↗

  These oranges have gone bad.
• 腐食ふしょくCommon
  noun, suru verb, transitive verb, intransitive verbDespite the gloss 'rot', this noun is really about corrosion and erosion — material eaten away, as metal is by rust or chemicals. For food or other matter rotting, くさる is the word you want.
  その神社じんじゃの腐食ふしょくの原因げんいんの一ひとつは酸性雨さんせいうである。↗

  The decay of the shrine is due, in part, to acid rain.

Use 「くさる」, the verb, when food or other organic matter rots, goes bad or decays; 腐食, though glossed 'rot', is really a noun for corrosion and erosion, chiefly of metal, not for spoiling food.

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

• くさるto rot
• 腐食ふしょくrot
• 朽ちるくちるto rot
• 腐れるくされるto spoil
• 腐朽ふきゅうdecay
• 膿うみcorruption