Concept
Extramarital sex occurs when a married person engages in sexual activity with someone other than their spouse. The term may be applied to the situation of a single person having sex with a married person. Where extramarital sexual relations do not breach a sexual norm, it may be referred to as consensual non-monogamy (see also polyamory). Where extramarital sexual relations do breach a sexual norm, it may be referred to as adultery or non-monogamy (sexual acts between a married person and a person other than the spouse), fornication (sexual acts between unmarried people), philandery, or infidelity. These terms imply moral or religious consequences, whether in civil law or religious law. American researcher Alfred Kinsey found in his 1950-era studies that 50% of American males and 26% of females had extramarital sex. Depending on studies, it was estimated that 26–50% of men and 21–38% of women, or 22.7% of men and 11.6% of women had extramarital sex. Other authors say that between 20% and 25% of Americans had sex with someone other than their spouse. Durex's Global Sex Survey (2005) found that 44% of adults worldwide reported having had one-night extramarital sex and 22% had an affair. According to a 2004 United States survey, 16% of married partners have had extramarital sex, nearly twice as many men as women, while an additional 30% have fantasized about extramarital sex. According to a 2015 study by Durex and Match.com, Thailand and Denmark were the most adulterous countries based on the percentage of adults who admitted having an affair. A 2016 study by the Institute for Family Studies in the US found that black Protestants had a higher rate of extramarital sex than Catholics. A 2018 US study found that 53.5% of Americans who admitted having extramarital sex did so with someone they knew well, such as a close friend. About 29.4% were with someone who's somewhat well-known, such as a neighbor, co-worker or long-term acquaintance, and the rest were with casual acquaintances.