1. 不足;不完备
The inadequacy of something is the fact that there is not enough of it, or that it is not good enough.

2. 不够格;能力不足;无法胜任
If someone has feelings of inadequacy, they feel that they do not have the qualities and abilities necessary to do something or to cope with life in general.

1. unsatisfactoriness by virtue of being inadequate

Synonym: inadequateness

2. lack of an adequate quantity or number

e.g. the inadequacy of unemployment benefits

Synonym: insufficiencydeficiency

3. a lack of competence

e.g. pointed out the insufficiencies in my report
juvenile offenses often reflect an inadequacy in the parents

Synonym: insufficiency