I didn't know, for instance, that polar bears have black skin, the better to retain heat.

They also have an insulated core to retain interior heat during the cold months.

And if your barbecue grill has a lid to retain heat, all the better.

It is used to retain heat close to the body, without the energy cost of heating the whole cabin.

Others tried ceramic parts to retain heat in the engine for higher efficiency.

The problem is that different parts of the body produce and retain heat at different rates.

The body's efforts to retain and produce heat continue until a new higher temperature is reached.

A Russian oven is designed to retain heat for long periods of time.

But remember that retained heat will continue to cook the fish after it has been removed from the grill.

Its atmosphere is far too thin to retain solar heat.