In legal definitions for interpersonal status, a single person is someone who is not in a relationship or is unmarried. In common usage, the term 'single' is often used to refer to someone who is not involved in any type of serious romantic relationship, including long-term dating, engagement, marriage, or someone who is 'single by choice'. Single people may participate in dating and other activities to find a long-term partner or spouse.
People may remain single for a variety of reasons, including financial and emotional or physical health issues, stress in the family, time constraints, education, career, personal preferences, advanced age or social fears, and living in a society or locality where there are an insufficient number of people of the preferred sex for romantic or sexual attraction. In some cases, single people may be uninterested in marriage, domestic partnership, or other types of committed relationships.
Certain careers and positions require that people remain single. Sometimes, this is coupled with celibacy or chastity, either for secular or for religious reasons, such as priests, nuns and monks in certain faiths. Loneliness can occur for some people who look for but cannot find anyone they might wish to date, especially for those suffering the loss of companionship following divorce or bereavement. Some single people, however, regard and appreciate solitude as an opportunity.
In some countries, particular laws may directly or indirectly disadvantage single persons. In the United States, for example, Social Security widow(er) benefits are only available to those persons who have been previously married, and single people in the United States pay more income taxes than married people. In many countries tour and holiday operators impose a penalty (often as much as 100%) on persons who travel alone.