Final answer:
Incest is defined as sexual contact between closely related individuals and is universally prohibited by the incest taboo. Laws and social norms about what constitutes an incestuous relationship can vary across cultures and jurisdictions.
Step-by-step explanation:
Incest is defined as sexual contact between individuals who are related to one another, typically close family members. This definition is consistant with the concept of the incest taboo, which is a universal cultural norm that prohibits sexual relationships between specific kinds of kin, especially between parents and their offspring, and sometimes extends to other relations considered too close for sexual relationships. Each culture may interpret which relationships are considered incestuous to varying degrees, but it is widely recognized that such norms support the social structure by delineating between potential marital partners and family members.
Moreover, incest can be connected to legal and social concepts, including kinship, family of procreation, and bilateral descent. Laws vary across different jurisdictions, such as in the United States where first-cousin marriage laws differ from state to state. The enforcement and recognition of such relationships can be significant in the context of family definitions used by institutions like the U.S. Census Bureau versus more sociological or anthropological definitions.