A deficiency is an insufficient amount of something. If you feel sluggish and tired all day, you might have an iron deficiency, meaning you aren't eating enough iron-rich foods.

You are most likely to hear the word deficiency in regard to health, like a sleep deficiency. But you can use deficiency to describe other kinds of lack — a deficiency of fun that occurred while your friends were out of town. Deficiency also means a failure or shortcoming, like a deficiency in math class, which might result in a notice from school — known as a deficiency — being mailed to your home.

Definitions of deficiency

n lack of an adequate quantity or number

inadequacy, insufficiency
adequacy, sufficiency
the quality of being sufficient for the end in view
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exiguity, leanness, meagerness, meagreness, poorness, scantiness, scantness
the quality of being meager
deficit, shortage, shortfall
the property of being an amount by which something is less than expected or required
scarceness, scarcity
a small and inadequate amount
the quality of being slight or inadequate
meagerness or poorness connoted by a superfluity of water (in a literary style as well as in a food)
restricted to bare necessities
oxygen deficit
temporary oxygen shortage in cells resulting from strenuous exercise
spareness, sparseness, sparsity, thinness
the property of being scanty or scattered; lacking denseness
dearth, paucity
an insufficient quantity or number
infrequency, rareness, rarity
noteworthy scarcity
Type of:
the relative magnitude of something with reference to a criterion

n the state of needing something that is absent or unavailable

“water is the critical deficiency in desert regions”
lack, want
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the state of being absent
dearth, famine, shortage
an acute insufficiency
a deficiency or failure in neurological or mental functioning
mineral deficiency
lack of a mineral micronutrient that is essential for normal nutrition or metabolism
the condition of being short of something
stringency, tightness
a state occasioned by scarcity of money and a shortage of credit
absence by virtue of not occurring
the state of being elsewhere than in particular place
a deficiency of iron; results from inadequate iron in the diet or from hemorrhage
Type of:
demand, need
a condition requiring relief

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