1. Unsatisfactoriness by virtue of being inadequate
   "The inadequacy of the resources hampered the project's progress";
   - inadequateness
    
2. A lack of competence
   "juvenile offences often reflect an inadequacy in the parents";
   - insufficiency
    
3. Lack of an adequate quantity or number
   "the inadequacy of unemployment benefits";
   - insufficiency, deficiency

Derived forms: inadequacies

Type of: amount, disadvantage, failing, minus, unsatisfactoriness, weakness

Antonym: adequacy, sufficiency