"露水，指在夜間通過冷凝從大氣中沉積下來的水蒸氣"，中古英語 deaw, deu，源自古英語 deaw，源自原始日耳曼語 *dawwaz（源頭還包括古撒克遜語 dau，古弗裏西亞語 daw，中古荷蘭語 dau，古高地德語 tau，德語 Tau，古諾爾斯語 dögg "dew"），或許源自 PIE 詞根 *dheu- "流動"（源頭還包括梵語 dhavate "流動，奔涌"）。
引申意義上用於指清新的事物（古英語晚期），或者暗示清晨和青春的新鮮（1530年代）。作爲動詞，指"用露水或像露水一樣弄溼"，古英語 deawian。
The formation of dew is explained by the loss of heat by bodies on the earth's surface through radiation at night, by which means they and the air immediately about them are cooled below the dew-point ....Dew is thus deposited chiefly on bodies which are good radiators and poor conductors of heat, like grass; hence also it appears chiefly on calm and clear nights--that is, when the conditions are most favorable for radiation. It never appears on nights both cloudy and windy. In winter dew becomes hoar frost. [Century Dictionary]
露水的形成是通過地面物體在夜間通過輻射失去熱量，從而使它們和周圍的空氣冷卻到露點以下來實現的。因此，露水主要沉積在良好的輻射體和熱導率較差的物體上，如草地； 因此，它主要出現在風平浪靜、晴朗的夜晚——也就是輻射條件最有利的時候。它從不出現在既多雲又有風的夜晚。在冬季，露水變成霜。[世紀詞典]
