Synastry

Synastry is the astrological technique for comparing two people's natal charts. The two charts are overlaid; the aspects between Person A's planets and Person B's planets describe the dynamics of their relationship — what flows, what grinds, what attracts, what repels. Strong synastry has dense aspects between personal planets (Sun, Moon, Mercury, Venus, Mars) — relationships with only outer-planet contacts can feel fated but distant. Close Venus-Mars contacts are the classic "chemistry" signature. Saturn contacts produce the gravitational pull of long-term commitment (or burden). Synastry is most useful as a description of dynamics, not a verdict on compatibility — every chart pair has both supportive and difficult contacts; what matters is which themes the couple chooses to grow into. Distinct from composite (which treats the relationship as a third entity) and transits (which describe the day-by-day weather).