Final answer:
The parents' definition of a family as a husband, wife, and child fits the description of a nuclear family, which is a small unit consisting of parents and children living together.
Step-by-step explanation:
The definition of a family comprising a husband, wife, and child refers to a nuclear family. This family structure is characterized by being the smallest unit, typically consisting of two parents and their immediate children living in the same household. The nuclear family contrasts with other types of family structures, such as extended families, which may include multiple generations like grandparents, aunts, uncles, and cousins, or blended families which involve a mix of stepparents and stepchildren, and single-parent or intergenerational families. In societal studies, sociologists tend to define family in various ways, either based on the structure, emotional connections, or economic alliances. However, for the purpose of this specific question, the nuclear family is the one that best fits the definition provided by the parents of the child on the pediatric unit.