Drekkana

Drekkana (Sanskrit: द्रेष्काण or द्रेक्काण) is one of the sixteen main vargas (divisions of a sign) described by Parasara to Maitreya who wanted to be explained about the different kinds of houses (Brihat Parasara Hora Sastra (Sl. VI.1). Parasara states that relationship with co-borns is to be judged from the drekkanas occupied by planets. All standard ancient texts on Hindu astrology describe these vargas. The actual disposition of a planet is properly known from its occupation of these sixteen vargas. These sixteen sub-divisional charts which are one of the four dimensions of astrology are a basic ingredient of Hindu astrology, and each sub-divisional chart is firstly required to be studied independently and then collectively as one. M. Ramakrishna Bhat is of the opinion that Drekkana is not a Sanskrit word but borrowed from the Greek.

Drekkana is one third equal part of a sign (Rasi) or 1/36th part of the Zodiac, the first part is ruled by the lord of the very sign that is referred to, the second part is ruled by the lord of the 5th sign from that sign and the third part is ruled by the lord of the 9th sign from the sign in question. However, Rudra states that some interpret the said Parasari rule as lords of the 5th and the 9th navamsas whereas the Kalpa Latha of Somanatha states that the twelve drekkanas from Mesha ('Aries') to Karaka ('Cancer') will have for their lords, the rulers of the twelve signs, in clock-wise symmetrical order from Mesha and similarly for the rest i.e. from Simha ('Leo') and from Dhaunus ('Sagittarius'). And, there is also the Parivritti Thrayapaksha method recommended in the Vriddha Karikas of Jaimini which suggests the lordship as per the scheme followed while erecting the Navamsa Chart.Varahamihira subscribes to the Parasari method and describes all thirty-six drekkanas (Brihat Jataka Ch.XXVII). A planet gains strength when it is in its own drekkana. He recommends the use of the drekkana occupied by the Sun at the time of query for ascertaining the lagna when the time of birth is not known.

...
Wikipedia