1. A metallic mixture, once considered an element, composed of neodymium and praseodymium.
2. A mixture of rare-earth elements and their oxides used chiefly in manufacturing and in coloring various forms of glass.
[From Greek didumos, twin, double (from the fact that it was usually found associated with the previously discovered lanthanum); see dwo- in the Appendix of Indo-European roots.]
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