Synastry is the practice of comparing the birth charts of two people for purpose of determining the dynamics that will arise in their relationship.

The word is derived from the Greek sunastria (συναστρία), which means something like “co-starred” or perhaps “star-crossed”.

Synastry is usually used for the purposes of determining the compatibility between two people who are in a romantic relationship, although it is often applied more generally in order to study the strengths and weaknesses of any generic type of relationship between two people, including business partnerships, family relationships, etc.

Relationship comparisons through synastry are usually accomplished by superimposing one person’s birth chart over another, either so that the planets of each are in the same wheel, or so there is one wheel just outside the other, allowing for quick comparison of where the planets in one person’s chart are relative to the the planets in the other person’s chart.

Since synastry involves the use of the birth chart, it is an extension of the branch of astrology known as natal astrology.

Books on Synastry

John Green, Do You Love Me? The Astrology of Relationships, MISPA Books, London, 2015.

Rod Suskin, Synastry: Understanding the Astrology of Relationships, Llewellyn Publications, Woodbury, MN, 2008.

Ronald Davison, Synastry, Understanding Human Relations Through Astrology (1977).

Francis Sakoian and Louis Acker, The Astrology of Human Relationships (1973).

Other Resources

A two-hour podcast on synastry with astrologer John Green: Synastry: The Astrology of Relationships