When something radiates, it sends out waves or rays. The sun radiates light and warmth.
If your house has a radiator, that might help you remember this word, because the radiator radiates warmth. Radiating is a concept that applies to anything that emits rays or waves. People camping make a fire so it can radiate light and heat. Our bodies radiate some heat, but not nearly as much as something as hot as a stove. If a nuclear reactor is damaged, it could radiate dangerous nuclear energy — or radiation.