Non-monogamyNon-monogamy (or nonmonogamy) is an umbrella term for every practice or philosophy of non-dyadic intimate relationship that does not strictly hew to the standards of monogamy, particularly that of having only one person with whom to exchange sex, love, and/or affection. In that sense, "nonmonogamy" may be accurately applied to extramarital sex, group marriage, or polyamory.
InfidelityInfidelity (synonyms include cheating, straying, adultery, being unfaithful, two-timing, or having an affair) is a violation of a couple's emotional and/or sexual exclusivity that commonly results in feelings of anger, sexual jealousy, and rivalry. What constitutes infidelity depends on expectations within the relationship. In marital relationships, exclusivity is commonly assumed. Infidelity can cause psychological damage, including feelings of rage and betrayal, low sexual and personal confidence, and even post-traumatic stress disorder.
Open marriageOpen marriage is a form of non-monogamy in which the partners of a dyadic marriage agree that each may engage in extramarital sexual relationships, without this being regarded by them as infidelity, and consider or establish an open relationship despite the implied monogamy of marriage. There are variant forms of open marriage such as swinging and polyamory, each with the partners having varying levels of input into their spouse's activities.
DatingDating is a stage of romantic relationships in which two individuals engage in an activity together, most often with the intention of evaluating each other's suitability as a partner in a future intimate relationship. It falls into the category of courtship, consisting of social events carried out by the couple either alone or with others. The meaning of the word dating shifted after the sexual revolution to include a more informal use referring to a romantic, sexual relationship itself beyond an introductory or trial stage, but prior to marriage.
AdulteryAdultery (from Latin adulterium; ad- + alterō, “I change/alter [one lineage for another”]) is extra-marital sex partaken by a spouse, or premarital sex partaken by a betrothed person, that is considered objectionable on social, religious, moral, or legal grounds. Although the sexual activities that constitute adultery vary, as well as the social, religious, and legal consequences, the concept exists in many cultures and shares some similarities in Christianity, Judaism and Islam.
PolyamoryPolyamory () is the practice of, or desire for, romantic relationships with more than one partner at the same time, with the informed consent of all partners involved. People who identify as polyamorous may believe in open relationships with a conscious management of jealousy and reject the view that sexual and relational exclusivity (monogamy) are prerequisite for deep, committed, long-term, loving relationships. Others prefer to restrict their sexual activity to only members of the group, a closed polyamorous relationship that is usually referred to as polyfidelity.