Final answer:
A nuclear family is composed of one or two parents and their immediate offspring. While the traditional nuclear family is less common in the United States, there are variations such as single-parent households, same-sex families, and cohabitation families.
Step-by-step explanation:
A nuclear family is composed of one or two parents and their immediate offspring. It is commonly found in small-scale foraging societies and industrial/post-industrial and market societies, where families frequently move. However, the traditional model of a nuclear family with married parents and children has become less common in the United States. Today, there are variations of the nuclear family, including single-parent households headed by a mother or father, same-sex families, and cohabitation families.