Synonyms for Three:

adj.

having three of something (adjective)
treble, triple.
triple (adjective)
thrice, threefold, Triform, treble, Triply, triune, tertiary.

n.

eight, eighty, cardinal number, five, crore, fifteen, fifty, eighteen, eleven, billion. triumvirate, triune, group, Triunity. artifact (noun)
trey.
three (noun)
ternary, trident, trine, trinity, deuce-ace, terzetto, trio, clover, tripod, tercet, triple, deltoid, triad, troika, trey, ternion, triangle, iii, trilogy, leash, delta, cardinal, 3, triptych, tierce, triplet, trimester.
three of something (noun)
trilogy, troika, trinity, triplet, ternion, triumvirate, trio, triad, ternary.
triune (noun)
triune.

Other synonyms:

III
iii.
triune, triumvirate, Triunity. Other relevant words:
iii, ternary, triumvirate, tierce, leash, terzetto, tertiary, triune, 3, ternion, Triunity, thrice, Triform, eleven, treble, eighty, trine, fifty, eight, trinity, five, tercet, cardinal number, cardinal, deuce-ace, trey.