synonymity

noun

1. (uncountable, usually)The state of being a synonym.

   “Mr. Ellis, who proposes a system with 117 notes within the octave, is^([sic]) thus shown that an infinite number of notes is required, for there is no synonymity in any system when the key-note moves.”

   “The wave of rebellion swept over me in an instant, beginning with an heretical doubt as to the sanctity of the established order of things[…]and ending in an adamantine determination to defend my honor and my life to the last ditch against the blind and senseless regulation which assumed the synonymity of misfortune and treason.”