from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A metallic mixture, once considered an element, composed of neodymium and praseodymium.
  • n. A mixture of rare-earth elements and oxides used chiefly in manufacturing and coloring various forms of glass.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A mixture of praseodymium and neodymium once thought to be an element (symbol Di).

from the GNU version of the Collaborative International Dictionary of English

  • n. 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.

from The Century Dictionary and Cyclopedia

  • n. 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.
  • n. [capitalized] A genus of fungi belonging to the Myxomycetes.


From Greek didumos, twin, double; see dwo- in Indo-European roots.
(American Heritage® Dictionary of the English Language, Fourth Edition)



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