halogen Meaning, Definition & Usage

  1. noun any of five related nonmetallic elements (fluorine or chlorine or bromine or iodine or astatine) that are all monovalent and readily form negative ions

WordNet

Hal"o*gen noun
Etymology
Gr. "a`ls, "alo`s, salt + -gen: cf. F. halogène.
Definitions
  1. (Chem.) An electro-negative element or radical, which, by combination with a metal, forms a haloid salt; especially, chlorine, bromine, and iodine; sometimes, also, fluorine and cyanogen. See Chlorine family, under Chlorine.

Webster 1913