Final answer:
A family can be defined as two or more people in an adaptable social and economic alliance that involves kinship, reproduction, and the care of offspring. Families vary across cultures and adapt to changing social and economic needs.
Step-by-step explanation:
A family can be defined as two or more people in an adaptable social and economic alliance that involves kinship, whether perceived through blood, marriage, or other permanent or semipermanent arrangement. It frequently, but not always, involves reproduction and the care of offspring and coresidence within the same locale. Families vary greatly across cultures and also adapt to changing social and economic needs. Sometimes families aggregate into larger units for short periods to meet challenging needs, such as eldercare, illness, job loss, transition between college and career, etc.