Extramarital Sex
Extramarital sex is sex occurring outside of marriage, usually referring to when a married person engages in sexual activity with someone other than their marriage partner. Generally there are moral as well as religious objections to sexual relationships by a married person outside of the marriage, which is often referred to in law or religion as adultery. Others may call it infidelity or "cheating".
In contrast, there are some cultures, groups or individual relationships in which extramarital sex is an accepted norm. In today's western cultures some people practice "polyamory", otherwise known as responsible non-monogamy, or "open marriage". The ethical practice requires honest dialogue and consent of those involved.
Read more about this topic: Sexual Ethics