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 3.0 & Open English WordNet

The halogens are a group in the periodic table consisting of six chemically related elements: fluorine, chlorine, bromine, iodine, astatine, and tennessine, though some authors would exclude tennessine as its chemistry is unknown and is theoretically expected to be more like that of gallium. Wikipedia

Group of chemical elements Wikidata

Any of the elements of the halogen family, consisting of fluorine, chlorine, bromine, iodine, and astatine. OmegaWiki

Any element of group 17, i.e. fluorine, chlorine, bromine, iodine and astatine, which form a salt by direct union with a metal. Wiktionary

Any element of group 17. Wiktionary (translation)