deficiency

deficiency — noun

1. a condition in which a person, a system, or a living thing has too little of som

1.nounB2
Definition

a condition in which a person, a system, or a living thing has too little of something necessary for healthy or proper operation

Example

Haruto's doctor told him he had an iron deficiency, so he started taking supplements.

deficiency + of [specific nutrient]

The soil in Naoko's garden had a mineral deficiency, and her vegetables grew very slowly.

Common collocations
  • iron deficiency
  • vitamin D deficiency
  • mineral deficiency
  • sleep deficiency
  • water deficiency
  • severe deficiency
  • mild deficiency
  • nutritional deficiency
Synonyms
  • shortage

    More concrete and usually refers to countable quantities (food, money, staff); 'deficiency' can also describe abstract or internal lacks

  • lack

    A more general and common word; 'lack' is neutral while 'deficiency' often implies that the missing amount is harmful

  • insufficiency

    More formal and technical; common in academic or medical writing

Antonyms
  • abundance

    An ample or more-than-adequate supply

  • surplus

    An extra amount beyond what is needed

Grammar Patterns

deficiency + of [substance]

deficiency + in [source / location / person]

Usage Note

Often used in medical and nutritional contexts, but also applies to systems, resources, and natural environments. Can be countable ('a vitamin deficiency') or uncountable ('a deficiency of resources').

Common Mistakes

He has a deficiency of confident.
He has a deficiency of confidence.
'deficiency of' should be followed by a noun, not an adjective.
The team suffered from a deficiency players.
The team suffered from a deficiency of players.
'deficiency of' needs the preposition 'of' before the noun.

2. a fault, weakness, or problem in someone's character, a plan, a system, or a pro

2.nounB2
Definition

a fault, weakness, or problem in someone's character, a plan, a system, or a product that makes it less effective or successful than it should be

Example

The project failed because of a serious deficiency in the original plan.

deficiency + in [plan / system]

Gabriel felt that his shyness was a deficiency that held him back at work.

Common collocations
  • structural deficiency
  • serious deficiency
  • major deficiency
  • deficiency in the plan
  • deficiency in the design
  • point out deficiencies
Synonyms
  • fault

    More specific; 'fault' often implies blame or responsibility, while 'deficiency' is more neutral and descriptive

  • weakness

    Softer and broader; 'weakness' can be inherent, while 'deficiency' suggests a gap relative to a standard

  • flaw

    Often used for design or physical defects; slightly more specific to objects than people

Antonyms
  • strength

    A positive quality or strong point

  • advantage

    A feature that puts something in a favourable position

Grammar Patterns

deficiency + in [plan / system / character / product]

Usage Note

Unlike sense 1, this sense focuses on quality or adequacy rather than quantity. It is frequently used with 'in' ('a deficiency in the design') and is common in evaluation contexts (reviews, inspections, performance assessments).

Common Mistakes

There is a deficiency of the system.
There is a deficiency in the system.
For faults or weaknesses, use 'deficiency in', not 'deficiency of'.
The plan has many lacks.
The plan has many deficiencies.
'Lack' is not typically used as a countable noun for individual faults; use 'deficiency' or 'weakness' instead.

Word family

Synonym discussion

Sense: noun/1

All four words describe a situation where something needed is missing or insufficient, but they differ in scope and formality. 'Shortage' is the most concrete and commonly refers to countable resources (food, water, staff): 'The city faced a water shortage after three months without rain.' 'Lack' is the broadest and most neutral, working for both concrete and abstract contexts: 'A lack of sleep made him irritable.' 'Deficiency' carries a stronger medical or nutritional implication and suggests that the missing amount is harmful to health or proper function: 'A vitamin C deficiency can cause scurvy.' 'Insufficiency' is the most formal and often appears in academic, legal, or official reports: 'The court cited an insufficiency of evidence to proceed.' 'Deficit' adds a numerical or financial dimension — it implies a measured shortfall relative to a target: 'The budget deficit reached ten million dollars.' For everyday conversation, 'lack' and 'shortage' are the safest choices; 'deficiency' works best in health, nutrition, and system-performance contexts.

shortage ↗lack ↗insufficiencydeficit ↗

Common collocations

Nouns

Adverbs

Phrases

  • suffer from a deficiency
  • a deficiency of something
  • a deficiency in something
  • correct a deficiency
  • diagnose a deficiency

Prepositions

Etymology

LatinFrenchEnglish

'Deficiency' comes from Latin 'dēficientia', meaning 'a failing, a want, a lack'. This noun was formed from the verb 'dēficere' — 'to fail, to run out, to be wanting' — which was itself built from 'dē-' (down, away) and 'facere' (to do, to make). The idea was literally 'to undo' or 'to let down', and over time the word shifted toward the sense of 'not having enough'. It entered English through French 'déficience' in the 1500s, first used in medical texts to describe a lack of bodily substances and later extended to any kind of shortfall or imperfection.