|the offspring of a zebra and a donkey.|
|a screen or mat covered with a dark material for shielding a camera lens from excess light or glare.|
|—the chemical symbol for|
|2.||astronomy right ascension|
|3.||(in Britain) Royal Academician or Academy|
|4.||(in Britain) Royal Artillery|
|5.||Argentina (international car registration)|
|[(sense 5) from República Argentina]|
|1.||Royal Agricultural Society|
|2.||Royal Astronomical Society|
The symbol for the element radium.
reticular activating system
The symbol for radium.
|radium (rā'dē-əm) Pronunciation Key
A rare, bright-white, highly radioactive element of the alkaline-earth group. It occurs naturally in very small amounts in ores and minerals containing uranium, and it is naturally luminescent. Radium is used as a source of radon gas for the treatment of disease and as a neutron source for scientific research. Its most stable isotope is Ra 226 with a half-life of 1,622 years. Atomic number 88; melting point 700°C; boiling point 1,737°C; valence 2. See Periodic Table.
Referred with Amendments Senate