Radiant: Giving Off Rays
Radiant means giving off light or heat, and also visibly happy. Both come from the Latin for a ray.
Radiant describes something giving off light, heat or energy in rays. The Latin *radius* means a ray or spoke, and physics keeps it precisely: *radiant heat* travels as infrared radiation and warms objects directly without heating the air on the way, which is why you feel the sun on a cold day.
- Giving off light or heat. *Radiant heat.*
- Visibly happy. *A radiant smile.*
- Radiate — to spread out from a centre. *Roads radiate from the square.*
Word forms
| Form | Word | Example |
|---|---|---|
| Adjective | radiant | A radiant glow. |
| Adverb | radiantly | Radiantly happy. |
| Noun | radiance | A soft radiance. |
| Verb | radiate | Radiate warmth. |
| Noun | radiation | Infrared radiation. |
How it is used in a sentence
- Underfloor heating works by radiant heat.Warming objects rather than air.
- She looked radiant.A conventional compliment.
- Pain radiating down the arm is a warning sign.Medical.
The ray family
- Radius — a ray, a spoke, and the line from a circle's centre
- Radiate — spread out from a centre
- Radiator — the heating panel, and the car's cooler
- Radiation — energy travelling as waves or particles
- Ray — the plain English word, from the same Latin
From Latin *radiantem*, shining, from *radiare*, to emit rays, from *radius*, a ray or spoke of a wheel. The bone in the forearm shares the name for its shape.
Radiant or radiated heat?
Radiant heat is the standard term for heat transferred by infrared radiation. Radiated is used of the process rather than the type.
Why is a car radiator called that?
Because early designs were thought to radiate heat away, though most of the cooling actually happens by convection through the air.