a form of energy that is transferred by a difference in temperature
make hot or hotter; "the sun heats the oceans"; "heat the water on the stove"
Hot weather conditions
A source or level of heat for cooking
hotness: the presence of heat
bath0596
On the righthand side of this photo you can see two small holes (vents) which lead to a room that has a very hot wood fire. The hot air from this fire would circulate under the tiled floor and heat it up. Basically a Roman version of central heating. The tiles were so hot that the Romans had to wear sandals when they walked into the room.
Koi pond extends under the floor
For heat and humidity control. Surface of pond is far smaller than the volume of water the koi have to live in. A wonderful symbiosis in design.