Se-lē'ni-ŭm, n.

n. [N. Lat., from Gr. σελήνη, the moon, so called from its resemblance to tellurium, from tellus, the earth.] (Chem.) An elementary substance, allied to sulphur, having a dark-brown color, with a metallic luster. It passes into vapor at 650° Fahrenheit, producing the odor of decaying horseradish. Graham.