any of two or more words or expressions in a language that are used with the same meaning, e.g. begin and start
synonymic /-ʹnimik/ adj
synonymical /-ʹnimikl/ adj
synonymity /-ʹnimiti/ noun
[Middle English sinonyme via Latin from Greek synōnymon, neuter of synōnymos synonymous, from syn- + onyma name]