04/04/17 Defective, Deficient; Deficiency, Defect

Defective Deficient Deficiency Defect

Similar but different:
A defective thing is faulty.
A deficient number or amount is insufficient.
Deficient may mean defective only in the sense that something is missing, not that the design is flawed. (When writing of due-process rights, for example, if notice is deficient it is also said to be defective.)
Watch out for the noun forms, too: don’t use deficiency (inadequate in number or amount) to mean defect (fault).