deficient
gb/dɪfˈɪʃənt/ us/dɪfˈɪʃənt/
B2
English
~ 8400
Senses
0 senses
adjective
B2
property
1
not having enough of something
Not having enough of something important or needed.
Usage pattern:
be deficient in [something]
Common mistake:
Learners sometimes use *deficient of* instead of *deficient in*. The usual pattern is *be deficient in [something]*, e.g. *The report is deficient in detail*, not *deficient of detail*.
Synonyms
lacking (More common and slightly simpler; often used in the same construction, e.g. 'lacking in confidence'.)
|
inadequate (Stronger criticism that something is not good enough in quality or amount.)
Antonyms
sufficient (Focuses on there being enough of something, the opposite of being short of it.)
|
adequate (Suggests just enough to meet a need, the opposite of falling below what is needed.)
Collocations
deficient in experience
|deficient in resources
|deficient performance
|deficient system
|morally deficient
|seriously deficient
Themes
evaluation
|work
|education
|daily life
|core_vocabulary
Examples
- The report was rejected because it was deficient in detail.
- Her training is deficient in basic safety procedures.
- The company’s security measures were found to be seriously deficient.
- The program is deficient in support for international students.
- His argument was interesting but ultimately deficient in evidence.
Learner examples
- My diet is deficient in fresh vegetables.
- The team is deficient in experienced players.
- This plan is deficient in clear goals.
- The school is deficient in modern computers.
- His speech was good but deficient in facts.
adjective
technical
B2
property
2
lacking a needed nutrient
Not having enough of an important nutrient or substance in the body.
Usage pattern:
be deficient in [a nutrient or substance]
Common mistake:
Learners sometimes say *have a deficient of iron* instead of using the adjective correctly. Say *be deficient in iron* or *have an iron deficiency*, not *have a deficient of iron*.
Synonyms
insufficient (General word for not enough; often used in technical reports about levels or amounts of substances.)
|
depleted (Suggests that the level has been used up or reduced over time.)
Antonyms
sufficient (Indicates that the level of the nutrient or substance is high enough for normal function.)
|
replete (Technical/medical term meaning fully supplied with a particular substance.)
Collocations
iron-deficient
|vitamin D-deficient
|nutrient-deficient diet
|iodine-deficient population
|nutritionally deficient
|deficient in calcium
Themes
health
|science
|medicine
|body
Examples
- Many people in northern countries are deficient in vitamin D during the winter.
- The test showed that he was severely deficient in iron.
- Children who are iodine-deficient may develop serious health problems.
- A diet that is deficient in calcium can lead to weak bones.
- Patients deficient in this enzyme cannot properly break down the drug.
Learner examples
- She is deficient in iron, so she takes pills.
- Many adults are deficient in vitamin D.
- His diet is deficient in protein.
- The doctor said I am deficient in this vitamin.
- If you are deficient in calcium, your bones can become weak.
adjective
archaic
C1
property
3
having low mental ability (offensive)
Having very low mental ability; an old word that is now offensive and should not be used about people.
Usage pattern:
be mentally deficient
Common mistake:
Learners may not realize that using *deficient* to describe a person’s mental ability is outdated and offensive. In modern English, avoid calling a person *deficient*; use respectful terms like *person with an intellectual disability* if needed.
Synonyms
intellectually disabled (Modern, more neutral and respectful term; used in formal and medical contexts instead of the outdated *deficient*.)
Antonyms
intelligent (Direct opposite in terms of mental ability.)
|
gifted (Suggests unusually high mental ability, the strong opposite of the old idea of being 'deficient'.)
Collocations
mentally deficient
|severely deficient child
|deficient in intelligence
|classified as deficient
Themes
health
|disability
|offensive_language
Examples
- The law, written in the 1950s, uses the term "mentally deficient," which is now considered offensive.
- Old medical records sometimes described patients as deficient in intelligence.
- The novel reflects the outdated belief that certain groups were inherently deficient.
Learner examples
- The phrase "mentally deficient" is old and offensive.
- Modern writers avoid calling a person deficient.
- In the past, some children were wrongly labeled as deficient.
- You should not describe a person as deficient in this way.
- The word is now mainly seen in old books as "mentally deficient".
Grammar
Dictionary form
deficient
IPA
GB/dɪfˈɪʃənt/
US/dɪfˈɪʃənt/
Syllables & stress
de - fi - cient (3 syllables)
Stress on 2nd syllable (fi)
Word forms
Adjective
- Base: deficient
Word family
Core family
deficiency
noun B2
Related words
deficit
noun B2
Negative and opposite forms
sufficient
adjective B1
insufficient
adjective B2
Advanced or less common
deficiently
adverb C1
Expressions
deficient in
1/dɪfˈɪʃənt ˈɪn/
fixed phrase
not having enough of something
Not having enough of a stated thing that is needed or wanted.
Examples
- Many young adults are deficient in savings for retirement.
- This essay is deficient in clear examples.
- The soil here is deficient in nutrients, so plants grow poorly.