deficient

What it means

1. Lacking something essential; often construed with in.

   My diet is deficient in vitamin D.

   2 more examples

   They were deficient in social skills.

   His voice is beautiful but deficient in power.

   Synonyms: absent, poor in, void of, absent, awanting, bereft of, deficient of, deprived of

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. mathematicsOf a number n, Having the sum of divisors σ(n) < 2n, or, equivalently, the sum of proper divisors (or aliquot sum) s(n) < n.

In a sentence

They were deficient in social skills.

Where it comes from

1. Latindeficiens
2. Englishdeficient

From Latin deficiens, present participle of deficere (“to lack, fail, be wanting”); see defect.