Quantcast
Merriam-Webster Logo
  • Dictionary
  • Thesaurus
  • Medical
  • Scrabble
  • Spanish Central
  • Learner's Dictionary

ionium

play
noun io·ni·um \ī-ˈō-nē-əm\

Definition of ionium

  1. :  a natural radioactive isotope of thorium having a mass number of 230



Origin of ionium

ion; from its ionizing action


First Known Use: 1907


Medical Dictionary

ionium

play
noun io·ni·um \ī-ˈō-nē-əm\

Medical Definition of ionium

  1. :  a natural radioactive isotope of thorium having a mass number of 230




Learn More about ionium

  1. Medical Dictionary: Definition of "ionium" Britannica.com: Encyclopedia article about "ionium"


Seen and Heard

What made you want to look up ionium? Please tell us where you read or heard it (including the quote, if possible).

WORD OF THE DAY

February 10, 2016

to put in good humor

Get Word of the Day daily email!

WORD GAMES

Take a 3-minute break and test your skills!

image1037863653

Which of the following refers to thin, bending ice, or to the act of running over such ice?

kittly-benders duvet pince-nez spindrift
Name That Thing

10 quick questions: hear them, spell them, and see how your skills compare to the crowd.

TAKE THE QUIZ
SCRABBLE® Sprint

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ