Synastry

Synastry is the astrological technique that compares two natal charts to study the relationship between two people. It looks at the aspects between the planets of one chart and those of the other, for example one person's Venus trine the other's Mars, and at which of the other person's houses each set of planets falls into. It is far more precise than comparing Sun signs alone, because it takes the whole chart into account. It is complemented by the composite chart, which describes the relationship as an entity of its own.