汚水（おすい、osui）
- sewage

The Japanese word 汚水 （おすい） means "sewage," "wastewater," or "polluted water." It refers to water that has been contaminated by human activities, such as domestic use, industrial processes, or agricultural runoff. This water typically contains waste materials, chemicals, and other pollutants.

⚫︎下水処理場で汚水を浄化します。 Translation: We purify the sewage at the sewage treatment plant. ⚫︎工場から汚水が排出されることによって、川が汚染された。 Translation: The river was polluted due to the discharge of wastewater from the factory. ⚫︎大雨で汚水が溢れ出した。 Translation: Sewage overflowed due to the heavy rain.

This word is used in formal and informal contexts to describe wastewater or sewage. It is commonly used in discussions about environmental issues, sanitation, and water treatment. The word 汚水 is also used in technical fields such as engineering and environmental science.

The word 汚水 is typically written with the kanji 汚 (よご-れる/kitanai - dirty, polluted) and 水 (みず - water). The reading is おすい. It is almost always written with kanji. There are no other common ways to write this word. The okurigana is fixed.

⚫︎排水（はいすい） - drainage; wastewater ⚫︎廃水（はいすい） - waste water; effluent

⚫︎清浄な水（せいじょうなみず） - clean water ⚫︎真水（まみず） - fresh water; pure water

この川は、生活《汚水によって汚染されています。》 ・Translation: This river is polluted by domestic sewage. ・Explanation: This sentence describes the source of the pollution in the river, linking it to residential wastewater.

《汚水の処理は、環境保護のために不可欠です。》 ・Translation: Sewage treatment is essential for environmental protection. ・Explanation: This sentence emphasizes the importance of managing wastewater to safeguard the environment.

The word 汚水 is formed from the kanji 汚 (よご-れる - to become dirty, polluted) and 水 (みず - water), literally meaning "polluted water." This directly reflects the word's meaning and the nature of the substance it describes.