The Threshold Between Two Domains
A cusp is a boundary degree — either between two houses or between two zodiac signs. The house cusp is the degree at which one house ends and the next begins. The sign cusp is the 0° of any sign — the degree at which the Sun transitions from one sign to the next (e.g., 0° Aries is the cusp between Pisces and Aries). Planets within 2–3° of a house cusp are considered to have influence in both houses; planets exactly on the cusp are fully read in the house they are entering.
Cusps in Practice
| Type | Meaning |
|---|---|
| Angular house cusps (1,4,7,10) | Most powerful — life direction markers |
| Sign cusp (0° of any sign) | Strongest expression of sign's new energy |
| Planet near a cusp | Influence in adjacent houses; check both |
The Sign Cusp and "Cusp Babies"
Popularly, "born on the cusp" refers to people born when the Sun is near a sign boundary — but this is a misnomer astrologically. The Sun is always in one sign, never between two. A person born on the day the Sun moves from Scorpio to Sagittarius is either a Scorpio or a Sagittarius, depending on the exact birth time. The cusp myth persists because people born at the boundary may absorb qualities of the adjacent sign through other chart factors — but the Sun sign itself is definite, not blended.