Polite noun for hot water, used in everyday contexts like cooking, bathing, or making tea.
Let's boil some water and make coffee.
Refers to a hot bath itself, often in phrases like お湯に入る or お湯につかる.
I boiled water in the kettle and made tea.
I fill the bathtub with hot water.
I'm tired, so I want to take a hot bath.
I got into the hot bath to warm up my cold body.
I poured hot water into the cup and made instant noodles.
I soaked slowly in the hot bath to relieve the day's fatigue.
Hot water comes out right away in this hotel room.
Polite prefix お- + 湯 (hot water). The prefix adds politeness and is standard in everyday speech.