What is the term used for a marriage within kin group, caste, or a group living in the same locality?

Endogamy

The correct answer is Option (4) → Endogamy

Endogamy (Option 4): This term is derived from the Greek words "endon," meaning "within," and "gamos," meaning "marriage." Endogamy involves marrying within a particular group, such as within the same kinship, caste, or community. The practice of endogamy is often influenced by social, cultural, or religious considerations and is a way to maintain social cohesion, preserve traditions, and reinforce social boundaries.

In the context of the provided options:

Polygyny (Option 1): Refers to a marital arrangement where a man has multiple wives simultaneously.

Polyandry (Option 2): Refers to a marital arrangement where a woman has multiple husbands simultaneously.

Exogamy (Option 3): Refers to the practice of marrying outside a specific social, cultural, or ethnic group. Exogamous marriages typically involve individuals from different communities or social backgrounds.

So, the correct option is [4].