noun, noun which may take the genitive case particle 'no'
warm water
Refers to water that is warm, not hot. Commonly used in contexts like heating, bathing, or swimming pools.
I like swimming in a heated pool.
I washed the vegetables with warm water.
Mix warm water and cold water to get the right temperature.
Warm water comes out right away in this hotel room.
I soothed my tired feet by soaking them in warm water.
This equipment supplies warm water to each floor.
冷水 is cold water, the direct opposite of 温水, which is warm water.
Compound of 温 (warm) and 水 (water). The reading is on'yomi for both characters.