/ ˈhælədʒən; NAmE / noun
( chemistry ) any of a set of five chemical elements, including fluorine , chlorine and iodine , that react with hydrogen to form acids from which simple salts can be made. Halogens, in the form of gas, are used in lamps and cookers / stoves.
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WORD ORIGIN
mid 19th cent.: from Greek hals , halo- salt + -gen .