Definition of rationality in English:

noun

• 1The quality of being based on or in accordance with reason or logic.

  ‘like any phobia, rationality plays only a small role’

  1. 1.1The quality of being able to think sensibly or logically.
     ‘Scott wanted to play the character with a bit more dignity and rationality’
  2. 1.2The quality of being endowed with the capacity to reason.
     ‘we call rationality the distinction of man, when compared with other animals’

• 2Mathematics
  The property of a number, quantity, or expression of being expressible, or containing quantities which are expressible, as a ratio of whole numbers.