Meaning
The kanji 腐 (腐) fundamentally signifies 'rot,' 'decay,' or 'spoil.' Its meaning isn't limited to physical deterioration; it also extends to 'corruption' or 'moral decay' when applied to abstract concepts like social systems or individuals. Additionally, it can describe the process of 'corrosion' in metals or even a state of being 'stale' or 'trite' for ideas.
This kanji's origin lies in a phono-semantic compound. On the left, it features the radical 肉 (にくへん - nikuhen), meaning 'flesh' or 'meat.' The right side, 府 (ふ - fu), primarily serves as the phonetic component, giving the 'fu' sound. Historically, 府 also carried meanings like 'mansion,' 'storehouse,' or 'government office.' The original form of 腐 was 𪪹, which clearly depicted both 府 and 肉.
This combination visually suggests 'flesh' left in a 'confined place' or 'storehouse' where it would inevitably 'decay.' In this way, the kanji strikingly illustrates organic matter undergoing decomposition. The 'meat' radical clearly points to the kind of substance that rots, while the phonetic component helps to reinforce the core concept of deterioration.
Comprising 14 strokes, 腐 is a Joyo kanji, meaning it's designated for common use. Although typically taught in Grade 8 within the Japanese school system, it is classified as N1 level for the JLPT, indicating its advanced recognition requirement for non-native speakers.
Readings
On'yomi (音読み) — Chinese-derived readings
The primary On'yomi for 腐 is フ (FU). These readings are generally used when 腐 appears as part of a compound word, combining with other kanji to form more complex meanings related to decay, spoilage, or corruption.
- 腐敗 (fuhai) — This term refers to decomposition, rot, or putrefaction, especially of organic matter. It's also widely used to describe corruption or moral decay within organizations, politics, or society.
Example: 食品の腐敗 (shokuhin no fuhai) — food spoilage
- 腐食 (fushoku) — This word specifically denotes corrosion or erosion, typically referring to the deterioration of metals or other materials due to chemical reactions.
Example: 金属の腐食 (kinzoku no fushoku) — metal corrosion
- 豆腐 (tōfu) — Meaning tofu or bean curd, this is an interesting compound. It literally translates to "rotted beans," which alludes to the traditional fermentation process involved in making tofu, historically perceived as a form of "rotting" or curdling.
Example: 冷奴の豆腐 (hiyayakko no tōfu) — chilled tofu
- 陳腐 (chimpu) — This compound describes something as stale, trite, hackneyed, or conventional. It often implies a lack of originality or freshness.
Example: 陳腐な考え (chimpu na kangae) — a stale or hackneyed idea
Kun'yomi (訓読み) — Native Japanese readings
Kun'yomi readings are native Japanese pronunciations, typically used when 腐 appears alone or with okurigana (trailing hiragana) as a verb or adjective.
- くさ.る (kusa.ru) — This is an intransitive verb meaning 'to rot,' 'to decay,' 'to spoil,' or 'to go bad.' It can apply to food, wood, or even abstract concepts like relationships or one's spirits (e.g., 気分が腐る to feel depressed).
Example: 魚が腐る (sakana ga kusaru) — the fish spoils
Example: 腐りかけ (kusarikake) — starting to rot, on the verge of spoiling
- くさ.らす (kusa.rasu) — This is a transitive verb meaning 'to let rot,' 'to spoil (something),' or 'to allow something to decay.' It implies actively causing or permitting something to deteriorate.
Example: 食料を腐らす (shokuryō o kusarasu) — to let food spoil (e.g., by forgetting it)
Common Words & Compounds
The kanji 腐 appears in a wide array of words and compounds, reflecting its diverse applications from literal decay to abstract notions of corruption and staleness. Here are some common examples categorized by theme:
Biological Decay & Food
- 腐敗 (fuhai) — decomposition, rot, putrefaction, corruption
- 腐る (kusaru) — to rot, to go bad, to spoil (intransitive)
- 腐りかけ (kusarikake) — on the verge of spoiling, half-rotten
- 豆腐 (tōfu) — tofu, bean curd (literally "rotted beans")
- 防腐剤 (bōfuzai) — preservative (an agent to prevent rotting)
- 腐葉土 (fuyōdo) — leaf mold, humus (decomposed leaf soil)
Corrosion & Erosion
- 腐食 (fushoku) — corrosion, erosion (e.g., of metal)
- 腐食性 (fushokusei) — corrosiveness, corrosive property
Moral & Societal Decay
- 腐敗政治 (fuhai seiji) — corrupt politics, political corruption
- 堕落腐敗 (daraku fuhai) — moral decay and corruption (a stronger expression)
Stagnation & Lack of Originality
- 陳腐 (chimpu) — stale, trite, hackneyed, outdated, conventional
- 陳腐化 (chimpuka) — becoming obsolete, making something stale
Example Sentences
冷蔵庫の中の牛乳が腐っていた。
Reizōko no naka no gyūnyū ga kusatte ita.
The milk in the refrigerator had spoiled.
雨が続くと、木材が腐食しやすくなる。
Ame ga tsuzuku to, mokuzai ga fushoku shiyasuku naru.
When it rains continuously, wood tends to decay or corrode easily.
古い慣習に固執すると、組織が腐敗する恐れがある。
Furui kanshū ni koshitsu suru to, soshiki ga fuhai suru osore ga aru.
If one clings to old customs, there is a risk of the organization becoming corrupt.
この物語は時代を経て少し陳腐に感じるようになった。
Kono monogatari wa jidai o hete sukoshi chimpu ni kanjiru yō ni natta.
This story has become a little stale over time.
彼は自分の人生を腐らせないよう、毎日努力している。
Kare wa jibun no jinsei o kusarasenai yō, mainichi doryoku shite iru.
He strives every day not to let his life go to waste.
豆腐は日本料理に欠かせない食材です。
Tōfu wa nihon ryōri ni kakasenai shokuzai desu.
Tofu is an indispensable ingredient in Japanese cuisine.
公園には腐葉土でできた豊かな土壌がある。
Kōen ni wa fuyōdo de dekita yutakana dojō ga aru.
The park has rich soil made of leaf mold.
この食品には鮮度を保つための防腐剤が加えられている。
Kono shokuhin ni wa sendo o tamotsu tame no bōfuzai ga kuwaerarete iru.
A preservative has been added to this food to maintain its freshness.
社会の腐敗を見て、彼は政治家になることを決意した。
Shakai no fuhai o mite, kare wa seijika ni naru koto o ketsui shita.
Seeing the corruption in society, he decided to become a politician.
湿気の多い場所では、金属が腐食する速度が速い。
Shikke no ooi basho de wa, kinzoku ga fushoku suru sokudo ga hayai.
In humid places, metal corrodes at a faster rate.
Memory Tip
To remember the kanji 腐, focus on its components: the left side is the 'meat' radical (肉, which often appears as 月 when on the left), and the right side is 府 (fu), meaning 'palace' or 'government office.' Picture a grand 'palace' (府) or a fancy storeroom where 'meat' (肉) has been carelessly forgotten and left to 'rot' or 'decay.' The striking contrast between the grandeur of the setting and the unsightly decay of the meat creates a powerful, memorable image. Alternatively, you can think of 'meat' (肉) that is no longer 'fit' for the 'office' or 'palace' (府) because it has 'spoiled.' This vivid mental story directly links the components to the kanji's core meaning of decay and corruption.