In Hindu society, the term gotra (Sanskrit: गोत्र) means clan. It broadly refers to people who are descendants in an unbroken male line from a common male ancestor or patriline. Generally the gotra forms an exogamous unit, with the marriage within the same gotra being prohibited by custom, being regarded as incest. The name of the gotra can be used as a surname, but it is different from a surname and is strictly maintained because of its importance in marriages among Hindus, especially among the higher castes. Pāṇini defines "gotra" for grammatical purposes as apatyam pautraprabhrti gotram (IV. 1. 162), which means "the word gotra denotes the progeny (of a sage) beginning with the son's son." When a person says "I am Kashyapa-gotra," he means that he traces his descent from the ancient sage Kashyapa by unbroken male descent. Among non-Brahmins, the gotras generally do not go back to sages, except in case of some communities such as Rajputs.