- a radioactive silvery-white metallic element of the actinide series. It occurs in several minerals including pitchblende, carnotite, and autunite and is used chiefly as a source of nuclear energy by fission of the radioisotope uranium-235. Symbol: U; atomic no: 92; atomic wt: 238.0289; half-life of most stable isotope, 238U: 451 × 109 years; valency: 2-6; relative density: 18.95 (approx.); melting pt: 1135°C; boiling pt: 4134°C
WordReference Random House Learner's Dictionary of American English © 2026
u•ra•ni•um /yʊˈreɪniəm/USA pronunciation
n. [uncountable]
WordReference Random House Unabridged Dictionary of American English © 2026- Chemistrya white, shining, radioactive, metallic element, used in atomic and hydrogen bombs and as a fuel in nuclear reactors.
u•ra•ni•um
(yŏŏ rā′nē əm),USA pronunciation n. [Chem.]
- Chemistrya white, lustrous, radioactive, metallic element, occurring in pitchblende, and having compounds that are used in photography and in coloring glass. The 235 isotope is used in atomic and hydrogen bombs and as a fuel in nuclear reactors. Symbol: U;
at. wt.: 238.03;
at. no.: 92;
sp. gr.: 19.07.
- Neo-Latin; see Uranus, -ium
- 1790–1800
Collins Concise English Dictionary © HarperCollins Publishers::
uranium /jʊˈreɪnɪəm/ n
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'uranium' also found in these entries (note: many are not synonyms or translations):
actinium
- advanced gas-cooled reactor
- astatine
- atomic bomb
- boiling-water reactor
- depleted uranium
- DU
- fission-track dating
- fluorine
- francium
- Free State
- fuel
- gas-cooled reactor
- Hahn
- intensifier
- Krugersdorp
- magnox reactor
- metamict
- neptunium
- New Mexico
- Orange Free State
- pile
- pitchblende
- plutonium
- polonium
- pressurized-water reactor
- promethium
- protactinium
- radioactive series
- radium
- samarskite
- Springs
- tellurium
- transuranic
- U
- uranium hexafluoride
- uranium series
- Urey
- actinium series
- actinouranium
- americium
- autunite
- carnotite
- coffinite
- curite
- dirty bomb
- enrich
- euxenite
- fertile
- fissile
