Webster's Revised Unabridged Dictionary · 1913

Europium

Europium , noun

[New Latin; Europe + -ium, as in aluminium.]

(Chemistry) A metallic element of the rare-earth group (Lanthanide series), discovered spectroscopically by Demarcay in 1896. Symbol, Eu; atomic number 63; at. wt., 151.965 (C=12.011); valence = +2 or +3.