What is a yoga in a birth chart?
A yoga in the birth chart is a combination of grahas, signs or houses that the classical texts describe with a stated effect. Yogas are rules, and the tool checks them as written.
What it is
Some yogas depend on the placement of grahas in houses from the Lagna, others on the placement from the Moon, and others on dignity or aspect. The rules and their lists differ between texts.
How it is worked out or read
This site checks nine standard yogas in the birth chart, and each shows whether its rule is met. Other yogas are described in their articles but are not yet checked by the tool.
Where it appears on this site
The yogas are shown in the birth chart. The Gajakesari article is one of the nine.
A named pattern
In chart reading, a yoga is a named combination of planets, signs and houses to which the classical texts assign a particular result. The word yoga means joining, and a chart yoga joins several factors into one recognisable pattern. A yoga may depend on a planet's sign, as in the Pancha Mahapurusha yogas; on the relationship between house lords, as in Raja and Dhana yogas; on the planets around the Moon, as in Sunapha and Anapha; or on the overall distribution of planets in the chart.
Not the panchang yoga
The chart yoga should not be confused with the yoga of the panchang, which is one of twenty-seven divisions based on the sum of the Sun's and Moon's longitudes and is one of the five limbs of the daily calendar. The two share a name but are unrelated. When reading an article or almanac, context usually makes clear which is meant.
Families of yogas
The texts list hundreds of yogas, but a few families account for most of those discussed. The Pancha Mahapurusha yogas are formed by Mars, Mercury, Jupiter, Venus or Saturn in its own or exaltation sign in a kendra. Lunar yogas such as Sunapha, Anapha, Durudhara and Kemadruma depend on planets in the second and twelfth from the Moon. Raja yogas join the lords of kendras and trikonas. Dhana yogas join the lords of wealth houses. And there are yogas of difficulty, such as Daridra yoga, and of cancellation, such as Neecha Bhanga.
How a reader uses them
A yoga highlights a theme in a chart, but its strength depends on the planets involved, their dignity and house, and whether cancellation conditions apply. Its results are also said to appear chiefly in the dashas of the planets that form it. So a reader notes the yogas, judges their strength, and then asks when they are likely to be active. The yoga check on this site's chart page tests nine standard rules and states each rule, leaving the weighing to the reader.
Avoiding the common mistakes
The commonest mistakes are to treat a yoga's name as its meaning, to count yogas as if more were better, and to ignore the conditions the texts themselves attach. The caution articles on yogas on this site discuss these in detail. Read with care, yogas are a useful vocabulary for patterns that recur across many charts.