ability vs inability

ability

noun
  • A unique power of the mind; a faculty. 

  • A skill or competence in doing; mental power; talent; aptitude. 

  • The quality or state of being able; capacity to do or of doing something; having the necessary power. 

  • Physical power. 

  • The legal wherewithal to act. 

inability

noun
  • Lack of the ability to do something; incapability. 

  • Lack of the option to do something; powerlessness. 

How often have the words ability and inability occurred in a corpus of books? (source: Google Ngram Viewer )