(uncountable) Inadequacy or incompleteness. / (countable) An insufficiency, especially of something essential to health.

Lacking something essential; often construed with in. / Insufficient or inadequate in amount.

A person who is deficient.

plural of deficiency

In a deficient manner.

(obsolete) Deficiency.

plural of deficience

The quality of being deficient.

plural of deficient

(medicine) any pathological effect in animals and humans due to a deficiency of boron in the diet / any of a number of disorders in plants that grow on granite, or other places deficient in boron