Endogamy is a rule of marriage which is intimately related to the caste structure. In Endogamy form of marriage, a person has to marry within his or her group or varna or caste or sub-caste.
For example, Brahmins have to marry Brahmins, Rajputs have to marry Rajputs, and Vaishya have to marry Vaishya, and so on.
A marathi will get married to a marathi, and a rajasthani will get married to a rajasthani.
Further, Brahmins of Karnataka are further subdivided into Smartha Brahmins and Madhya Brahmins and these sub-castes are also endogamous.
In the same way, Okkaligas, i.e., one of the dominant castes of Karnataka, are subdivided into Hallikars, Nonabas, Gangadigars, Kunchudigars, and so on.
Each one of these sub-castes is again endogamous.
Thus, an Okkaliga has to marry not only an Okkaliga girl but also in his own endogamous group whether it is Hallikar or Nonaba or any other as the case may be.
Endogamous jatis also exist among Sikhs, Jains, Christians and Muslims. Among some Gujarati castes there is strict spatial delimitation of the endogamous field.