lack — something missing or needed: After he left, they really felt the lack.
impotence — the condition or quality of being impotent; weakness.
inability — lack of ability; lack of power, capacity, or means: his inability to make decisions.
inadequacy — Also, inadequateness [in-ad-i-kwit-nis] /ɪnˈæd ɪ kwɪt nɪs/ (Show IPA). the state or condition of being inadequate; insufficiency.
incapacity — lack of ability, qualification, or strength; incapability.
incompetence — the quality or condition of being incompetent; lack of ability.
ineffectiveness — not effective; not producing results; ineffectual: ineffective efforts; ineffective remedies.
ineptness — without skill or aptitude for a particular task or assignment; maladroit: He is inept at mechanical tasks. She is inept at dealing with people.
stupidity — the state, quality, or fact of being stupid.
weakness — the state or quality of being weak; lack of strength, firmness, vigor, or the like; feebleness.
clumsiness — awkward in movement or action; without skill or grace: He is very clumsy and is always breaking things.
inanity — lack of sense, significance, or ideas; silliness.
