Definition of "diathesis"

diathesis

/daɪˈaθəsɪs/

noun
countable and uncountable, plural diatheses
1. (medicine) A hereditary or constitutional predisposition to a disease or other disorder.
  Quotations
  Medical materialism seems indeed a good appellation for the too simple-minded system of thought which we are considering. […] All such mental over-tensions, it says, are, when you come to the bottom of the matter, mere affairs of diathesis (auto-intoxications most probably), due to the perverted action of various glands which physiology will yet discover.
  1902, William James, “Lecture I”, in The Varieties of Religious Experience: A Study in Human Nature […] , New York, N.Y.; London: Longmans, Green, and Co. […]
  When a coal miner developed the eye disease nystagmus, was this to be diagnosed as due to work conditions or to an inherent constitutional diathesis?
  1997, Roy Porter, The Greatest Benefit to Mankind, Folio Society, published 2016, page 611
2. (grammar) Voice (active or passive).