dys·pro·si·um (dĭs-prōzē-əm, -zhē-əm)
n. Symbol Dy
A soft, silvery metallic element of the lanthanide series occurring in the minerals monazite and bastnaesite, used in nuclear reactor control rods and in the manufacture of laser materials and compact discs. Atomic number 66; atomic weight 162.50; melting point 1,412°C; boiling point 2,567°C; specific gravity 8.551; valence 3. See Periodic Table.
[New Latin, from Greek dusprositos, difficult to approach (from its rarity in nature) : dus-, dys- + prositos, approachable (from prosienai, to approach : pros-, toward + ienai, i-, to go; see ei- in the Appendix of Indo-European roots).]
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