tierce vs ternion

tierce and ternion both are nouns.

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

As nouns, tierce and ternion are synonyms defined as:

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

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

tierce (noun)	ternion (noun)
one of three equal parts of a divisible whole	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
the third canonical hour; about 9 a.m.