radium

noun

ra·​di·​um ˈrā-dē-əm 

often attributive

: an intensely radioactive metallic chemical element that occurs in combination in minute quantities in minerals (such as pitchblende or carnotite), emits alpha particles and gamma rays to form radon, and is used chiefly in the treatment of cancer and in radiographic devices see Chemical Elements Table

Examples of radium in a Sentence

Recent Examples on the Web

Radioactivity is a natural process where some atoms – like uranium, thorium and radium – break down on their own, releasing energy. —André O. Hudson, The Conversation, 26 June 2025

Brine can contain elevated levels of heavy metals like lead and arsenic, and often so much radium that, under certain Environmental Protection Agency guidelines, it would be classified as radioactive waste. —Justin Nobel, Harper's Magazine, 2 Jan. 2025

The radium lume on the hour markers and hands have developed a rich orange patina, which some people call Pumpkin or Caramel. Passport: Explore the finest destinations and experiences around the world in the Forbes Passport newsletter. —Thomas Wojtowicz, Forbes.com, 3 Apr. 2025

Measuring 38 mm in diameter, its Oyster case featured no crown guards and was fitted with a bidirectional, rotating Bakelite bezel with luminescent radium indices. —Oren Hartov, Robb Report, 28 Mar. 2025

Word History

Etymology

New Latin, from Latin radius ray

First Known Use

1898, in the meaning defined above

Phrases Containing radium

• radium therapy

Rhymes for radium

• stadium
• palladium
• vanadium

Kids Definition

radium

noun

ra·​di·​um ˈrād-ē-əm 

: a strongly radioactive shining white metallic element that is chemically similar to barium, occurs in combination in very small quantities in minerals (as pitchblende), and is used in the treatment of cancer see element

Medical Definition

radium

noun

ra·​di·​um ˈrād-ē-əm 

often attributive

: an intensely radioactive shining white metallic element that resembles barium chemically, that occurs in combination in minute quantities in minerals (as pitchblende or carnotite) principally as the isotope of mass number 226 formed from uranium 238, having a half-life of 1620 years, and emitting alpha particles and gamma rays to form radon, and that is used chiefly in luminous materials and in the treatment of cancer

—symbol Ra see Chemical Elements Table