In general, gotra denotes all persons who trace descent in an unbroken male line from a common male ancestor. Panini defines gotra for grammatical purposes as 'apatyam pautraprabhrti gotram', which means 'the word gotra denotes the progeny (of a sage) beginning with the son's son. In days gone by the Gotra was the basis of deciding matrimonial alliances. In order to avoid inbreeding persons from the same clan or Gotra were forbidden to marry.

Many lines of descent from the major rishis were later grouped separately. Accordingly, the major gotras were divided into ganas (subdivisions) and each gana was further divided into groups of families. The term gotra was then frequently started being applied to the ganas and to the sub-ganas.

Every Brahmin claims to be a direct descendant of one of the founding rishis of a certain gana or sub-gana. It is the gana or sub-gana that is now commonly referred to as gotra.

When a person says ' I belong to Gautam-gotra' he means that he traces his descent from the ancient sage Gautam by unbroken male descent.

According to the Baudhayanas rauta-sutra Vishvamitra, Jamadagni, Bharadvaj, Gautam, Atri, Vasishth, Kashyap and Agastya are 8 sages; the progeny of these eight sages is declared to be Gotras. This enumeration of eight primary gotras seems to have been known to Panini. The offspring (apatya) of these eight are gotras and others than these are called ' gotra vayava '.

Gotra of Idhar Vyas family is Gautam.