Predictive Techniques
Synastry
Astrology meaning, traditional reading, and frequently asked questions.
Quick Definition
The technique of comparing two birth charts to study the relationship between two people.
What Synastry Means
Synastry is the astrological technique of comparing two natal charts to study the relationship between two people. Each person’s planets are placed in the other person’s chart, and the aspects formed between the two charts are read as the texture of their connection. Synastry has been part of astrology since at least the Hellenistic period and was used historically to assess compatibility for marriage, business, and political alliances. Modern synastry, popularised by astrologers like Stephen Arroyo and Liz Greene, focuses heavily on emotional and psychological compatibility.
How to Spot Synastry in Your Chart
To work with Synastry, you compare your natal chart against the technique’s calculated chart or current planetary positions. Most astrology software generates Synastry charts automatically once your natal chart is set up — the comparison is the core of the technique.
Predictive work always reads both the natal chart and the Synastry layer together. The natal chart is the foundation; the Synastry layer describes how that foundation activates in time. Astrologers look for contacts between the two — planets that fall on natal degrees, aspects that form across the comparison — and read those contacts as the active themes.
Concrete Example
When one person’s Venus sits on another person’s Ascendant in synastry, astrologers traditionally read it as immediate attraction — the Ascendant person experiences the Venus person as beautiful, the Venus person feels welcomed and seen.
What Synastry Traditionally Indicates
Predictive astrology has been part of the craft since its earliest forms. Hellenistic astrologers used profections and primary directions; medieval astrologers refined firdaria and Persian techniques; modern astrologers added secondary progressions, solar arcs, and the systematic study of transits. Synastry sits within this long lineage of timing techniques.
The modern shift in predictive work, traceable through Dane Rudhyar and Liz Greene, is the move from event prediction toward psychological description. Rather than telling someone what will happen, modern predictive work tells them what theme is active and gives them language for working with it. The techniques are the same; the application has matured.
Frequently Asked Questions
What is the most important aspect in synastry?
Astrologers vary, but Sun–Moon, Venus–Mars, and any planet to the angles (Ascendant, Descendant, Midheaven, IC) are usually treated as most defining. Sun–Moon describes core compatibility; Venus–Mars describes attraction; angles describe how visible the connection is.
Does synastry predict whether a relationship will work?
It describes the texture of the connection — what the two people experience together — but it does not predict outcome. Two charts can show tremendous chemistry and still face structural challenges; two charts with little obvious chemistry can build deep partnerships. Astrology describes; it does not decide.
How is synastry different from a composite chart?
Synastry compares two charts side by side. A composite chart merges two charts into a single new chart that represents the relationship itself as its own entity. They are complementary techniques.
Do I need birth times for synastry?
Birth times help a great deal because they let the astrologer use accurate Ascendants, Midheavens, and house placements. Without birth times you can still compare planet-to-planet aspects, but the angle and house dimension is lost.
Related Terms
Other glossary entries that connect to Synastry:
Composite Chart
A single chart created by averaging two birth charts — represents the relationship itself as an independent entity.
Seventh House
The house of partnership — marriage, business partners, and open enemies; begins at the Descendant.
Transit
A planet’s current movement and the aspects it makes to your natal chart — the foundation of predictive astrology.
See Synastry in Your Own Chart
Definitions are easier to internalise when you can see them in your own birth chart. Calculate yours free — it places every term on this page into the concrete geometry of your own life.