Most people are married and married people have the most sex. Sexual activity in young single people tends to be sporadic, but is greater in industrialised countries than in developing countries.
A marriage is a relationship between or among individuals, usually recognized by civil authority and/or bound by the religious beliefs of the participants. The fact that marriage often has the dual nature of a binding legal contract plus a moral promise can make it difficult to characterize.
A married couple can be called each other’s spouses, and spousal is used as a legal term for the marital relation. A royal married couple are consorts.
In one form or another, marriage is found in virtually every society. The very oldest records that refer to it speak of it as an established custom. Despite attempts by anthropologists to trace its origin (and test the hypothesis of primitive promiscuity), evidence is lacking.
In Western societies, marriage has traditionally been understood as a monogamous union, while in other parts of the world polygamy has been a common form of marriage. Usually this has taken the form of polygyny (a man having several wives) but a very few societies have permitted polyandry (a woman having several husbands).
— The Lancet