Etymology From Latin deficiens, present participle of deficere (“to lack, fail, be wanting”); see defect.
1
Lacking something essential; often construed with in.
They were deficient in social skills.
2
Insufficient or inadequate in amount.
Apothecia lecanoroid; multilocular; each cell containing a single theke; paraphyses deficient.1882, Edward Tuckerman, Henry Willey, A Synopsis of the North American Lichens (part 1)
3
Mathematics, Sciences Of a number n, Having the sum of divisors σ(n)<2n, or, equivalently, the sum of proper divisors (or aliquot sum) s(n)<n.
Etymology From Latin deficiens, present participle of deficere (“to lack, fail, be wanting”); see defect.
1
A person who is deficient.
This was justified by the rationale that mental deficients, by definition, are not able to succeed in society.2004, Steven Noll, James Trent, Mental Retardation in America: A Historical Reader, page 316: