Both marriage and a family may be defined differently—and practiced differently—in cultures across the world. People's concepts of marriage and family in the United States are changing.

Increases in cohabitation, same-sex partners, and singlehood are altering our ideas of marriage. While most children still live in opposite-sex, two-parent, married households, that is no longer viewed as the only type of nuclear family

family — socially recognized groups of individuals who may be joined by blood, marriage, or adoption and who form an emotional connection and an economic unit of society. marriage — a legally recognized contract between two or more people in a sexual relationship who have an expectation of permanence about their relationship. cohabitation — the act of a couple sharing a residence while they are not married. nuclear family — two parents (traditionally a married husband and wife) and children living in the same household.