Introduction
Suppose Mars sits in a sign of Venus (Vrishabha or Tula) while Venus sits in a sign of Mars (Mesha or Vrishchika). Each planet is in the other's home. This is called parivartana, an exchange of signs.
In an exchange the two houses become closely tied: the lord of one house sits in the other and takes on its matters, and vice versa. That is why the texts treat it as a yoga of its own.
The rule
According to Phaladeepika (6.32): when the lords of two houses occupy each other's houses, the action is called parivartana. Between the lords of the twelve houses there are 66 such pairs.
ePandit names each pair by its houses, for example "exchange between the lords of the 4th and 10th". A planet that rules two signs (Mars, Venus, Mercury, Jupiter, Saturn) can join an exchange through either of them; ePandit names the houses actually exchanged.
Three groups: maha, khala, dainya
Phaladeepika divides the 66 pairs into three groups:
| Group | Which pairs | Count |
|---|---|---|
| Dainya | involving the lord of the 6th, 8th or 12th | 30 |
| Khala | involving the lord of the 3rd (without 6, 8, 12) | 8 |
| Maha | all others (between 1, 2, 4, 5, 7, 9, 10, 11) | 28 |
These are old category names, not a label on a person.
What tradition associates with them
Phaladeepika (6.33-34) gives results for these groups, which today are read calmly like this:
- Maha exchange: the text links it with the blessings of Lakshmi, fine clothes and ornaments, authority and the comfort of family. Tradition reads it as a leaning towards prosperity and responsibility.
- Khala exchange: the text describes ups and downs: at one time going astray, at another gentle in speech; at times prosperity returning, at times hardship. In other words, there is always room to recover.
- Dainya exchange: the text links it with a restless mind and interruptions to undertakings. Tradition holds that patience and careful steps help in such phases.
These are leanings, not fixed outcomes. Which houses are joined and the planets' condition change the picture a great deal.
Special exchanges in BPHS
BPHS counts some exchanges directly as raja yogas:
- An exchange between kendra and trikona lords (34.11-12) is a raja yoga. For example, for a Mithuna lagna, Mercury in Kumbha and Saturn in Kanya.
- An exchange between the lagna lord and the 5th lord (39.6-7) is called a "maha raja yoga" in BPHS.
ePandit shows these under parivartana and also in the raja yoga section.
How ePandit shows it
Each exchange is shown with the two planets, the two houses, the group (maha, khala or dainya) and the source. In the Mithuna lagna example above, Saturn also rules the 8th (Makara), but the exchange runs between Kumbha (9th) and Kanya (4th); so ePandit names it an exchange of the 4th and 9th lords and adds a note that Saturn also rules the 8th.
An exchange needs a birth time, because the houses are counted from the lagna.