inefficiency (n.)

• disability
• disablement
• disqualification
• imbecility
• inability
• inadequacy
• inaptitude
• inaptness
• inattentiveness
• incapability
• incapacity
• incompetence
• incompetency
• ineffectiveness
• ineffectuality
• ineptitude
• ineptness
• infancy
• inferiority
• insufficiency
• maladjustment
• maladroitness
• mediocrity
• minority
• rustiness
• thoughtlessness
• unfitness
• unskillfulness
• wardship