Meaning
The kanji 汚 covers dirty, filth, unclean, to pollute, and to defile. It shows up in everyday Japanese for physical dirtiness — a stained shirt, muddy shoes, polluted water — and extends to moral and social corruption, such as a disgraced reputation or a bribery scandal.
Structurally, 汚 combines two parts: the radical 氵 (sanzui, the three-dot water radical) on the left, and 亏 on the right, which historically conveyed the idea of falling short or being deficient. Together they evoke water that has been tainted — water that falls short of being clean. Contaminated water is the original image this kanji was built around.
The kanji has 6 strokes and is taught at the Grade 6 level in Japanese elementary school. While learners encounter it formally at N3, the adjective 汚い (きたない) — "dirty" or "messy" — is one of the first descriptive words Japanese children pick up. Its range runs from the mundane (dirty laundry, a muddy floor) to the serious (environmental pollution, political corruption). For example, both 汚染 (おせん, contamination) and 汚い部屋 (きたないへや, a messy room) use the same kanji.
In Sino-Vietnamese (Hán-Việt), this character is read as Ô. It maps directly to words like ô nhiễm (pollution) and ô uế (defilement) — the same character, the same core meaning, carried into Vietnamese through centuries of shared classical writing.
Readings
On'yomi (音読み) — Chinese-derived readings
The on'yomi readings オ and ウ appear in formal compound words (熟語, jukugo), most commonly in academic, environmental, legal, and political contexts. オ is by far the more productive reading and appears in the most important N3-level compounds.
- 汚染 (osen) — pollution, contamination. Essential for reading news about environmental issues.
- 汚職 (oshoku) — corruption, bribery (literally "defiled duty"). Frequently seen in political reporting.
- 汚水 (osui) — sewage, dirty water. Used in civil engineering and environmental contexts.
- 汚名 (omei) — dishonor, disgrace, tarnished reputation.
- 汚点 (oten) — a stain, a blemish (both literal and figurative).
- 汚物 (obutsu) — filth, waste matter, sewage.
Kun'yomi (訓読み) — Native Japanese readings
The kun'yomi readings appear in native Japanese verb and adjective forms — the ones you hear most in daily speech. Each reading fills a distinct grammatical slot: transitive verb, intransitive verb, adjective, or morally weighted verb.
- よご・す — transitive verb, "to make dirty, to soil, to stain." Example: 服を汚す (fuku wo yogosu) — to get one's clothes dirty.
- よご・れる — intransitive verb, "to become dirty, to get soiled." Example: 手が汚れる (te ga yogoreru) — one's hands get dirty.
- きたな・い — i-adjective, "dirty, messy, filthy, mean-spirited." The most conversational form. Example: 汚い部屋 (kitanai heya) — a messy room.
- けが・す — to defile, to desecrate, to dishonor. Carries a stronger moral or sacred weight than よごす. Example: 名誉を汚す (meiyo wo kegasu) — to dishonor one's reputation.
- けが・れる — to become defiled, to be tainted (intransitive, morally weighted). Example: 心が汚れる (kokoro ga kegareru) — for one's heart to become corrupted.
Common Words & Compounds
Environmental & Physical Contamination
- 汚染 (osen) — pollution, contamination (air, water, soil)
- 汚水 (osui) — sewage, dirty/polluted water
- 汚物 (obutsu) — waste matter, filth, sewage
- 環境汚染 (kankyō osen) — environmental pollution
- 大気汚染 (taiki osen) — air pollution
Social & Moral Disgrace
- 汚職 (oshoku) — corruption, bribery
- 汚名 (omei) — dishonor, infamy, tarnished name
- 汚点 (oten) — stain, blemish (on one's record or character)
- 汚名返上 (omei henjō) — clearing one's name, restoring one's reputation
Everyday Dirtiness
- 汚れ (yogore) — dirt, a stain, grime (noun)
- 汚れ物 (yogoremono) — dirty laundry, soiled items
- 汚い (kitanai) — dirty, messy, mean (i-adjective)
- 汚らしい (kitanarashii) — looking dirty, slovenly
Example Sentences
子供たちは泥で服を汚して帰ってきた。
Kodomotachi wa doro de fuku wo yogoshite kaette kita.
The children came home with their clothes dirtied by mud.
この川は工場の廃水で汚染されている。
Kono kawa wa kōjō no haisui de osen sarete iru.
This river is polluted by wastewater from the factory.
テーブルが汚れているので、拭いてください。
Tēburu ga yogorete iru node, fuite kudasai.
The table is dirty, so please wipe it.
彼は汚職で逮捕された政治家だ。
Kare wa oshoku de taiho sareta seijika da.
He is a politician who was arrested for corruption.
汚い手で食べ物を触らないで。
Kitanai te de tabemono wo sawaranaide.
Don't touch the food with dirty hands.
大気汚染が深刻な問題になっている。
Taiki osen ga shinkoku na mondai ni natte iru.
Air pollution has become a serious problem.
この一件は彼女の経歴に汚点を残した。
Kono ikken wa kanojo no keireki ni oten wo nokoshita.
This incident left a stain on her career record.
神社を汚すような行為は許されない。
Jinja wo kegasu yō na kōi wa yurusarenai.
Actions that desecrate a shrine cannot be forgiven.
洗濯機で汚れ物を洗うのを忘れた。
Sentakuki de yogoremono wo arau no wo wasureta.
I forgot to wash the dirty laundry in the washing machine.
彼は汚名を返上するために必死で働いた。
Kare wa omei wo henjō suru tame ni hisshi de hataraita.
He worked desperately to clear his tarnished name.
Memory Tip
Picture a water source (氵) that has been tainted. The three water drops on the left are normally pure, but something has gone wrong on the right side — the water falls short of its natural state. Think of a factory pipe draining sludge into a once-clear stream: that image of water being defiled is exactly what 汚 represents. For the adjective form 汚い (きたない), try this hook: "Kita nai? — Did something dirty come from the north (北, kita)?" — a playful way to lock in the reading. For the moral sense (けがす), think of a sacred shrine being "caged" in filth — the ke-ga sound suggests something precious being wrongfully touched.