a chemical element. Selenium is a grey substance that is used in making electrical equipment and coloured glass. A lack of selenium in the human body can lead to illnesses such as depression. 硒(化学元素,用于制造电气设备和有色玻璃,人体缺此元素可致抑郁等病) Word Originearly 19th cent.: modern Latin, from Greek selēnē ‘moon’.