ternion vs tercet

ternion and tercet both are nouns.

Word	Noun	Adjective	Verb	Adverb
ternion	Yes	No	No	No
tercet	Yes	No	No	No

As nouns, ternion and tercet are synonyms defined as:

ternion and tercet: the cardinal number that is the sum of one and one and one

Other synonyms of ternion include 3, deuce-ace, III, leash, ternary, terzetto, three, threesome, tierce, trey, triad, trine, trinity, trio, triplet, troika.

ternion (noun)	tercet (noun)
the cardinal number that is the sum of one and one and one	the cardinal number that is the sum of one and one and one