Whom they marry may be influenced by socially determined rules of incest, prescriptive marriage rules, parental choice and individual desire.
In some areas of the world, arranged marriage, child marriage, polygamy, and sometimes forced marriage, may be practiced as a cultural tradition.
Since the late twentieth century, major social changes in Western countries have led to changes in the demographics of marriage, with the age of first marriage increasing, fewer people marrying, and more couples choosing to cohabit rather than marry.
For example, the number of marriages in Europe decreased by 30% from 1975 to 2005.
Conversely, such practices may be outlawed and penalized in parts of the world out of concerns of the infringement of women's rights, or the infringement of children's rights (both female and male children), and because of international law.
The act of marriage usually creates normative or legal obligations between the individuals involved, and any offspring they may produce or adopt.
The related word "matrimony" derives from the Old French word matremoine, which appears around 1300 CE and ultimately derives from Latin mātrimōnium, which combines the two concepts: mater meaning "mother" and the suffix -monium signifying "action, state, or condition".
In The History of Human Marriage (1922), Edvard Westermarck defined marriage as "a more or less durable connection between male and female lasting beyond the mere act of propagation till after the birth of the offspring." In The Future of Marriage in Western Civilization (1936), he rejected his earlier definition, instead provisionally defining marriage as "a relation of one or more men to one or more women that is recognized by custom or law".
Some cultures allow the dissolution of marriage through divorce or annulment.
In some areas, child marriages and polygamy may occur in spite of national laws against the practice.