Cusp

Definition

A cusp is a boundary in an astrological chart. Most precisely, it is the degree marking the beginning of a house, such as the Ascendant at the First House cusp or the Midheaven in systems where it begins the Tenth House. In popular astrology, “being on the cusp” often refers to a birth date near the transition between two zodiac signs.

Astrological Meaning

House cusps show where particular areas of life begin within the chart. The sign on a house cusp, its ruling planet, and any planets located near that boundary can help describe how the house’s topics are approached. Interpretation varies with the chosen house system, since cusp degrees may change. A sign cusp works differently: planets occupy specific zodiac degrees and are normally placed in one sign rather than treated as a blend of two. Someone born near a solar sign change may still identify with the neighboring sign because of Mercury, Venus, the Ascendant, or other chart factors.

Why It Matters

Accurate cusp calculation helps astrologers assign planets to houses and identify each house ruler. This makes birth time, location, zodiac, and house system especially important. When a planet lies close to a house cusp, astrologers may compare techniques before deciding which house receives the strongest emphasis. Checking the complete natal chart usually gives a clearer interpretation than relying on a generalized sign-cusp label.

Related Encyclopedia Entries

• Traditional Astrology
• Astrological Terminology
• Natal Chart