Decan

Each of the twelve zodiac signs spans 30 degrees of the circle, and astrologers have divided that stretch into three 10-degree decans since ancient Egypt and the Hellenistic era. The first decan expresses the sign's nature in its purest form; the second and third are traditionally "colored" by the influence of the other two signs of the same element, or by the ruling planet of a neighboring sign — depending on the system used (Egyptian, Vedic, or Western). In practice, this means two people with the Sun in Libra can share the sign's core traits (a pull toward balance, diplomacy) yet express them quite differently depending on which decan their Sun falls in: the first decan of Libra reads more classically "Libran," while the third already carries notes of Aquarius. A decan is a layer of detail that comes after the basic "sign" and adds nuance without overriding the main archetype. For self-knowledge, decans are useful whenever a sign's general description feels "not quite you" — the explanation is often hiding in the third of the sign rather than a wrong horoscope.