Source : Webster's Revised Unabridged Dictionary (1913)

Cointension \Co`in*ten"sion\, n.
   The condition of being of equal in intensity; -- applied to
   relations; as, 3:6 and 6:12 are relations of cointension.

         Cointension . . . is chosen indicate the equality of
         relations in respect of the contrast between their
         terms.                                   --H. Spencer.