A deficiency is a lack of something... Example : there is a deficiency of oxygen in the air :\

• In mathematics, a deficient number is a number n for which ?(n) < 2n.
  • In medicine there are a variety of nutrient deficiencies:
    • Avitaminosis is a deficiency of vitamins.
    • Boron deficiency (medicine)
    • Chromium deficiency
    • Iron deficiency (medicine)
    • Iodine deficiency
    • Magnesium deficiency (medicine)
    • Micronutrient deficiency
  • In construction, a deficiency is an item or condition that is considered sub-standard or below minimum expectations, such as those mandated by either drawings or specifications or the building code or the fire code, and/or any combination of the foregoing. Deficiencies are routinely discussed and dealt with in construction site meetings.
  • In genetics, a genetic deletion is also called a Deficiency.
  • In Real estate law, a deficiency in the ability to pay off a debt is also called a deficiency judgment or deficiency judgement.
  de:Mangel nl:Deficiëntie no:Mangel