House Cusp

A cusp is a technical but important term: the zodiac degree marking the start of each of the twelve astrological houses. House systems (Placidus, Koch, whole sign, and others) each define these boundaries differently, so the same planet can land in the sixth house under one system and already in the seventh under another, especially if it sits close to the edge. The cusps of the first, fourth, seventh, and tenth houses have special names — the Ascendant, the IC (lower culmination), the Descendant, and the Midheaven (MC) — and are considered the chart's strongest points. When a planet sits exactly on a cusp, its influence spreads across both life spheres the boundary divides, and the reading becomes more layered than a simple "planet in a house." For self-knowledge, a cusp is a reminder that a natal chart isn't made of rigid walls: boundaries are fluid, and even technical precision in the calculation doesn't remove the need to look at the whole picture rather than a single isolated detail.