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washing one's hands; water (or basin, etc.) for washing one's hands
restroom; lavatory; toilet
hand-washing (laundry, etc.)
食事の前に手洗いをしてください。
Please wash your hands before eating.
この服は手洗いが必要なので気をつけて。
This clothing requires hand washing.
食事の前に手洗いをする習慣をつけよう。
Let's make a habit of washing our hands before meals.