Deficient means lacking something that is needed. Vitamin deficient, deficient in iron, a deficient design.
It takes in. In medicine it is precise and testable: being deficient in a vitamin is a measurable state, and vitamin D deficiency is common at northern latitudes in winter. Applied to a design or a plan it means falling short of the requirement.
1adjectivedeficientLacking something that is needed.
“The inspectors found the school's fire safety arrangements seriously deficient.”
deficient is a state.
The Latin is to fail or fall short, the same falling short behind a defect. Something deficient has a defect in the amount of it.
hooks ontodefect
Latin deficiens comes from deficere, to fail or lack — de plus facere, to do.
Proto-Indo-European
*dʰeh₁-
Latin
deficiens
English, today
deficient
Built from
From Latin deficiens, present participle of deficere (“to lack, fail, be wanting”); see defect.
Etymology from Wiktionary, CC BY-SA