Radioactive

How to spell radioactive

11 letters · 5 syllables

How to pronounce radioactive

Say the part in capitals loudest.

What does radioactive mean?

1. adjectiveEmitting energy in the form of particles or rays from the unstable nuclei of atoms.

Radioactive in a sentence

• The plant stores its spent radioactive fuel in deep concrete pools.

• Workers wore badges that measured their exposure to radioactive material.

Where does radioactive come from?

Language of origin: Latin

This word was assembled from scientific Latin roots at the very end of the nineteenth century. The first half, radio-, derives from the Latin radius, which literally meant a 'ray', a 'spoke of a wheel', or a 'beam of light', and which had already given chemists the noun 'radiation' for energy travelling outward in rays. The second half, active, comes from the Latin agere, meaning 'to do' or 'to drive', so the whole word describes a substance that actively gives off rays. The term entered English around 1898, closely tied to the pioneering work of Marie and Pierre Curie on uranium and the new elements they isolated; Marie Curie herself is credited with popularising 'radioactivity'. Because it is a transparent compound, the spelling is regular: the trap is simply remembering the joining vowels, the 'io' of radio- meeting the 'a' of active to give radio-active.

How the word is built

• radio- (relating to rays/radiation, from Latin radius: ray)
• act (from Latin agere: to do, drive)
• -ive (adjective suffix)