Gotra
According to the Brihadaranyaka Upanisad 2.2.6, Gautama and Bharadvāja, Viśvāmitra and Jamadagni, Vashishtha and Kaśhyapa, and Atri are seven sages (also known as Saptarishi). The descendants of these eight sages are said to be gotras. This explanation  of the eight primary gotras seems to have been known to Pāṇini. Descendants of others are called gotrâvayava.