The Great Astrology Glossary
Triplicity: A group of three zodiac signs belonging to the same element. The fire triplicity is Aries, Leo, and Sagittarius; the earth triplicity is Taurus, Virgo, and Capricorn; the air triplicity is Gemini, Libra, and Aquarius; and the water triplicity is Cancer, Scorpio, and Pisces.