Definition of halogen in English:



  • 1Any of the elements fluorine, chlorine, bromine, iodine, and astatine, occupying group VIIA (17) of the periodic table. They are reactive non-metallic elements which form strongly acidic compounds with hydrogen from which simple salts can be made.

    • ‘Metals high on the activity series react more vigorously with oxidants including the halogens and the hydronium ion than those lower on the scale.’
    • ‘Four important chemical family names of elements still widely used are the alkali metals, the alkaline earths, the halogens, and the noble gases.’
    • ‘For many syntheses, this means using such compounds as hydrocarbons and alcohols, plus inorganic acids, metals, halogens, or other compounds.’
    • ‘Silicon behaves somewhat similarly to carbon, but compounds of silicon and hydrogen or silicon and the halogens (the silanes) are much more reactive than their carbon counterparts.’
    • ‘The oxidation number of the halogens other than fluorine is - 1, unless they are bonded to oxygen or a more electronegative halogen.’
    1. 1.1as modifier Denoting lamps and radiant heat sources using a filament surrounded by the vapour of iodine or another halogen.
      ‘a halogen bulb’
      • ‘In this treatment, the patient is secured to a dentist chair with leather straps and an extremely hot halogen lamp is left inches from their face for hours at a time.’
      • ‘Since most grooming occurs at night, high power halogen lights provide ample vision both front and rear while heated outside rear view mirrors allow for constant visibility.’
      • ‘The light source was a microscope halogen lamp, which unilaterally illuminated the protruding stump, via a light guide at a site 2-4 cm from the lower cut end.’
      • ‘Both Ceuta and Melilla are now surrounded by 10-foot fences studded with guard towers and movement sensors, topped with barbed wire and halogen searchlights.’
      • ‘The light source was a halogen lamp and light intensity was varied with neutral density filters.’


Mid 19th century: from Greek hals, halo- ‘salt’ + -gen.