From earlier inhability (“disqualification for office”), equivalent to in- +‎ ability. Compare Middle French inhabilité, Medieval Latin inhabilitās.

• IPA^(key): /ˌɪnəˈbɪlɪti/

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inability (countable and uncountable, plural inabilities)

1. Lack of the ability to do something; incapability.
   • 1720, John Shaw, “Of Religion”, in The Fundamental Doctrines of the Church of England,[…], volume I, London: […] George Strahan,[…] William Mears,[…], page 36:

     […] tho' theſe ſeem'd to be very unfit Inſtruments for compaſſing of that great Deſign for which they were then employ'd, becauſe of their Inability and Uncapacity in performing the Work ſo very great and important; […]

   • 2013 November 26, Daniel Taylor, “Jack Wilshere scores twice to ease Arsenal to victory over Marseille”, in The Guardian‎^[1]:

     The Premier League leaders did what many people thought was beyond them in their last European excursion, at the home of Borussia Dortmund, and they made light work of overcoming Marseille on a night when the one-sidedness was not reflected by their inability to add to Jack Wilshere's two goals.

2. Lack of the option to do something; powerlessness.

• unability