Advanced Concepts
Stellium
Three or more planets clustered in one sign or house - concentrated energy.
A stellium is a powerful concentration of planetary energy in one area of your chart. Most astrologers define it as 3+ planets in the same sign or house (some require 4+). This creates an intense focus in that life area - it becomes a major theme you can't ignore. The sign or house containing the stellium often dominates your personality or life experience.
Example
A stellium in the 7th house suggests relationships are a central theme, with many planets coloring how you partner.