noun
Refers to heated water, often contrasted with 水 (cold water). Used in cooking, bathing, and general contexts.
See also: 水 (みず)
お湯を沸かしてコーヒーを入れましょう。
Let's boil some hot water and make coffee.
この薬はお湯で飲んでください。
Please take this medicine with hot water.
noun
Often refers to a hot bath at home, a public bath (銭湯), or a hot spring (温泉). The honorific prefix お is frequently added.
疲れたから、お湯にゆっくり浸かりたい。
I'm tired, so I want to soak in a hot bath for a while.
この旅館の湯はとても気持ちがいい。
The hot spring at this inn feels really good.
noun
Technical use in metalworking and foundry contexts. Not an everyday meaning.
溶鉱炉から湯が流れ出る。
Molten iron flows out from the blast furnace.
水 is cold or room-temperature water, while 湯 is specifically hot water.
風呂 refers to the bath or bathroom as a place or facility, while 湯 emphasizes the hot water itself.
温泉 specifically means a natural hot spring resort or the spring water, whereas 湯 can refer to any hot bath or hot spring water more generally.
The kanji 湯 is a phono-semantic compound: the water radical 氵 (さんずい) combined with the phonetic component 昜 (よう), which also carries a meaning of 'rising sun' or 'warmth'. The reading ゆ is a native Japanese word (kun'yomi) for hot water.