Main Entry: ¹hal·o·gen

Pronunciation: \ˈha-lə-jən\

Function: noun

Etymology: Swedish, from hal- + -gen

Date: 1842

: any of the five elements fluorine, chlorine, bromine, iodine, and astatine that form part of group VIIA of the periodic table and exist in the free state normally as diatomic molecules

— ha·log·e·nous \ha-ˈlä-jə-nəs\ adjective