Definition of Selenium 1. A toxic nonmetallic element related to sulfur and tellurium; occurs in several allotropic forms; a stable grey metallike allotrope conducts electricity better in the light than in the dark and is used in photocells; occurs in sulfide ores (as pyrite) Noun Synonyms for word "selenium" Semanticaly linked words with "selenium" Hyponims for word "selenium" etymology nonselenium etymology radioselenium etymology selenium etymologically related Selene is derived from hydroselenic acid is derived from metallic selenium is derived from selane is derived from selen- is derived from selenate is derived from seleniate is derived from selenic acid is derived from selenide is derived from seleniferous is derived from selenio- is derived from selenious acid is derived from selenite is derived from selenium cell is derived from selenium dioxide is derived from selenium eye is derived from selenium hydride is derived from selenium oxide is derived from selenium sulfide is derived from selenium sulphide is derived from seleniuretted is derived from seleno- is derived from selenous is derived from selenyl