radiate

Radiate is a verb with several related senses. In physics and everyday language, to radiate means to emit energy, particles, or waves from a source, often in all directions. Objects with temperature above absolute zero radiate heat; lamps and stars radiate light; radio transmitters radiate radio waves. Less literally, to radiate can describe something spreading outward from a central point, such as spokes radiating from the hub or a pattern in a flower.

The word derives from Latin radius meaning ray or spoke. It entered English in the medieval period and has since broadened to include both physical emission and figurative uses such as "to radiate confidence" or "to radiate warmth."

In science, radiation covers a broad range of phenomena, from infrared heat to visible light and from radio waves to X-rays. Emission can be thermal, as in blackbody radiation, or non-thermal, as in radiation from energetic particles or nuclear decay. Radiative energy can travel through a vacuum or a medium, and it may be absorbed, reflected, or transmitted.

In contrast to radiate, the related verb irradiate means to expose something to radiation, often for sterilization or treatment.

In everyday language and metaphor, radiating qualities such as calm, happiness, or hostility can be described as extending outward from a person or object. Related terms include radiation, radiance, radiative transfer, and irradiance.