triplicity

[trih-plis-i-tee] /trɪˈplɪs ɪ ti/
noun, plural triplicities.
1.
the quality or state of being triple; threefold character or condition.
2.
a group or combination of three; triad.
3.
Astrology. the division of the signs of the zodiac into four groups of three signs each, the fire signs, the earth signs, the air signs, and the water signs, with each sign separated from others within the group by 120 degrees of the ecliptic.
Compare element (def 12).
Origin
1350-1400; Middle English triplicite < Late Latin triplicitās threefold state. See triplex, -ity
British Dictionary definitions for triplicity

triplicity

/trɪˈplɪsɪtɪ/
noun (pl) -ties
1.
a group of three things
2.
the state of being three
3.
(astrology) any of four groups, earth, air, fire, and water, each consisting of three signs of the zodiac that are thought to have something in common in their nature
Word Origin
C14: from Late Latin triplicitās, from Latin triplex threefold; see triplex