• Webster's Revised Unabridged Dictionary
    • n Didymium (Chem) A rare metallic substance usually associated with the metal cerium; -- hence its name. It was formerly supposed to be an element, but has since been found to consist of two simpler elementary substances, neodymium and praseodymium. See Neodymium, and Praseodymium.
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Century Dictionary and Cyclopedia
    • n didymium Chemical symbol, D or Di. A supposed element announced by Mosander in 1841, so named from being, as it were, the twin brother of lanthanum, previously discovered in the same minerals which yielded didymium, and from whose compounds those of didymium are separated with much difficulty. The most recent investigations indicate that didymium is not an element, but a mixture of several different elements.
    • n didymium [capitalized] A genus of fungi belonging to the Myxomycetes. The sporangia have a double wall, which is covered externally with crystals of lime, either scattered or compacted into a separable crust.
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Chambers's Twentieth Century Dictionary
    • n Didymium dī-dim′i-um a supposed element discovered in 1841, so named from being, as it were, twin brother of lanthamum.
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Webster's Revised Unabridged Dictionary
NL., fr. Gr. twin


In literature:

Oxide of Didymium, DO.
"A System of Instruction in the Practical Use of the Blowpipe" by Anonymous
DIDYMIUM ANELLUS, Morgan, n. sp.
"The Myxomycetes of the Miami Valley, Ohio" by A. P. Morgan
The rare metals cerium, lauthanum, and didymium have been lately investigated by Drs.
"The Galaxy, Volume 23, No. 2, February, 1877" by Various
It suggests a didymium in its form and habit, but is near a badhamia.
"The North American Slime-Moulds" by Thomas H. (Thomas Huston) MacBride
Didymium chlorid c. p., in 3-gram doses, was fed to a rabbit weighing 1,020 grams.
"Barium, A Cause of the Loco-Weed Disease" by Albert Cornelius Crawford
Lanthanum and Didymium discovered by Mosander.
"The Progress of Invention in the Nineteenth Century." by Edward W. Byrn