The requirements are simple, although they vary from state to state. In general, a man and a woman wishing to marry must obtain a license in the state in which they wish to be married, usually from a county clerk, a city clerk, or a a clerk of court. The fee usually is low.

Parties who wish to marry must have the capacity to do so. This means that neither can be married to someone else, the parties must be of a certain age, and both must understand that they are being married and what it means to be married. If, because of drunkenness, mental illness, or some other problem, one of the parties lacks capacity, the marriage will not be valid.

A few states require the man and the woman to have blood tests for venereal disease before the license is issued, although most do not require a blood test. In states that require a blood test, some will not issue a license if one or both of the parties have venereal disease, while others will allow the marriage if the couple knows the disease is present.

In a few states, a couple must show proof of immunity or vaccination for certain diseases or completion of a general physical examination.

Close blood relatives cannot marry, although in some states, first cousins can marry. Of those states that allow first cousins to marry, a few states also require that one of the cousins be unable to conceive children.

Some states require a waiting period, generally three days, between the time the license is issued and the time of the marriage ceremony.

Marriage is a private bond between two people, but it is also an important social institution. Most states define marriage as a civil contract between a man and a woman to become husband and wife.

The moment a man and a woman marry, their relationship acquires a legal status. Married couples have financial and personal duties to each other during marriage and after separation or divorce. State laws determine the extent of these duties. As the U.S. Supreme Court said about marriage in 1888: "The relation once formed, the law steps in and holds the parties to various obligations and liabilities."

Society recognizes marriage in several ways:

• As a way to express commitment, strengthen intimate bonds, and provide mutual emotional support.
• As a (comparatively) stable structure within which to raise children.
• As a financial partnership in which spouses may choose from a variety of roles. Both spouses may work inside or outside the home to support the family, or the husband may support the wife, or the wife may support the husband.

As our society becomes more complex, there is no longer a short answer to the question "What is marriage?" Definitions and opinions of the proper functions of marriage continue to change. The women's rights movement and gay rights movement have resulted in more equal treatment of men and women and the creation of new legal relationships, including domestic partnerships and civil unions for same-sex couples. The traditional concept of marriage remains, but it continues to evolve.