Final answer:
Finding a universal definition for the terms family and marriage is challenging due to the diversity of societal and cultural perspectives, and the evolving nature of social structures.
Step-by-step explanation:
The editors of your book in the Introduction of "Marriage, Family, and Kinship," argue that finding a universal definition for terms like family and marriage is challenging. This difficulty arises because sociologists and various cultures have diverse perspectives on what constitutes a family. While some may consider family as a group connected by blood, marriage, or adoption, others broaden this definition to include cohabitation relationships and fictive kin. Moreover, social institutions like marriage and family continuously adapt to societal changes, reflecting variations such as cohabitation, same-sex partnerships, and single-parent households. This diversity makes the quest for a universal definition complex and culturally sensitive.