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Each sign belongs to one of four elements: Fire, Earth, Air, Water. Traditionally, Fire and Air signs are considered compatible with each other, as are Earth and Water.
Each sign has a modality (Cardinal, Fixed, Mutable), which describes the sign's approach to life (initiating, stabilizing, or adapting).
Every Sun sign is said to be "ruled" by a particular planet or luminary. That planetary energy influences the sign's style or focus.
Aries: Bold, impulsive, action-oriented.
Taurus: Steady, sensual, security-driven.
Gemini: Communicative, curious, adaptable.