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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.

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

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.

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.

"The word didymium comes from a Greek word meaning "twin," because it was closely associated with the element lanthanium, both of which were found with cerium."

neodymium    praseodymium