Definition of didymium in English:


Line breaks: di¦dym|ium
Pronunciation: /dɪˈdɪmɪəm


[mass noun] Chemistry
A mixture containing the rare earth elements praseodymium and neodymium, used to colour glass for optical filters. It was originally regarded as a single element.
More example sentences
  • In 1879 Paul-Emile Lecoq, gallium's discoverer, announced that there was another element contaminating didymium, which he called samarium.
  • The discovery of praseodymium is credited to the Austrian chemist Carl Auer who found that a previously discovered element, didymium, was actually a mixture of two other new elements.
  • Didymia, and its supposed elemental associate, didymium, then vanished from the chemical pantheon.


mid 19th century: from Greek didumos 'twin' (because it was closely associated with lanthanum) + -ium (used as a suffix for new metals).

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