Parivartana

Parivartana ('exchange') occurs when two grahas each occupy a sign ruled by the other, for example Mars in Tulā and Venus in Meṣa. BPHS counts it, alongside conjunction and mutual aspect, as a sambandha (relationship) between the two grahas, and Phaladeepika ch. 6 divides exchanges into three classes: Mahā, Khala (involving the 3rd lord) and Dainya (involving the 6th, 8th or 12th lord).