Marriage or wedlock is an interpersonal relationship with governmental, social, or religious recognition. It is often created as a contract or through civil processes. Civil marriage is the legal concept of marriage as a governmental institution. The most common form of marriage unites one man and one woman as husband and wife. Other forms of marriage also exist: for example, polygamy in which a person takes more than one spouse is common in many societies. In some jurisdictions civil marriage has been expanded to include same-sex marriage. People marry for many reasons, but usually one or more of the following: legal, social and economic stability; the formation of a family unit; procreation and the education and nurturing of children; legitimizing sexual relations; public declaration of love; or to obtain citizenship.