Triplicity is one of the many factors that astrologers evaluate to gain an understanding of the strength and support that a planetary placement has. Like exaltation and fall, this is one of the five essential dignities and part of a complex ancient zodiacal rulership and co-rulership system.

Each triplicity, or element, in astrology is ruled by three planets, the order of which varies according to sect, meaning whether the chart in play is a day or a night chart. Triplicity allows us to see group support for the placement in question by assessing the placement and dignity of the triplicity rulers.

For example, if we are assessing the condition of Venus in Aquarius in a night chart, our triplicity rulers for the Air element are, in order, Mercury, Saturn, and Jupiter. Assessing these planets in the chart and their relation to Venus will inform us of her support network. This allows us to better evaluate, and add nuance to our understanding of the nature of the placement, particularly the group or social support piece.

This scheme above is attributable to Dorotheus of Sidon, a 1st-century Hellenistic astrologer, though there are variations of it that exist. Like all astrological techniques, we do not use this technique on its own, but as part of a larger toolkit that we employ to make deductions about placements in any chart that we look at.