Synonymity

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.

Source: wiktionary

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.

Source: wiktionary

Quine explains, without giving a definition, a concept of synonymity which is different from and presumably stronger than L-equivalence. He says: "The notion of synonymity figures implicitly also whenever we use the method of indirect quotations. In indirect quotation we do not insist on a literal repetition of the words of the person quoted, but we insist on a synonymous sentence; we require reproduction of the meaning. Such synonymity differs even from logical equivalence; and exactly what it is remains unspecified."

Source: wiktionary