Radiation

How to spell radiation

9 letters · 4 syllables

How to pronounce radiation

Say the part in capitals loudest.

What does radiation mean?

1. nounEnergy that travels outward from a source as waves or particles, including heat, light, or nuclear emissions.

Radiation in a sentence

• The safety inspector measured the radiation levels near the reactor.

• Sunscreen helps protect skin from harmful ultraviolet radiation.

Where does radiation come from?

Language of origin: Latin

This word traces back to the Latin radius, which literally meant a ray of light, the spoke of a wheel, or a straight rod or staff. From radius the Romans formed the verb radiare, meaning 'to emit rays' or 'to shine outward', and from that came the noun radiatio, describing the act of beaming or shining. English took the word in during the early 1600s, at first to describe the spreading of light or heat outward from a central source. As physics matured in the nineteenth and twentieth centuries, the meaning broadened to cover all kinds of energy travelling through space, including the invisible rays studied by pioneers like the Curies. The same radius root survives in everyday relatives such as 'radius', 'radio', and 'ray', a useful reminder that the spelling keeps the 'radi' core intact before the familiar '-ation' ending.

How the word is built

• radi- (ray, from radius)
• -ate (verb-forming)
• -ion (noun-forming suffix denoting an action or process)