synonymity noun. 
[sɪnǝ'nɪmɪti] L19.[from SYNONYMOUS + -ITY.]1.  The quality or fact of being synonymous or having the same meaning; = 
SYNONYMY 4. 
L19.2.  transf. Identity of nature of things having different names. 
L19.  [TahlilGaran] English Dictionary ▲