Affair

An affair is a sexual relationship, romantic friendship, or passionate attachment between two people without the other spouse knowing.

Romantic affair
A romantic affair, also called an affair of the heart, may refer to sexual liaisons among unwed or wedded parties, or to various forms of nonmonogamy. Unlike a casual relationship, which is a physical and emotional relationship between two people who may have sex without expecting a more formal romantic relationship, an affair is by its nature romantic.

Affair may also describe part of an agreement within an open marriage or open relationship, such as Swinging, dating, or polyamory, in which some forms of sex with one's non-primary partner(s) are permitted and other forms are not. Participants in open relationships, including unmarried couples and polyamorous families, may consider sanctioned affairs the norm, but when a non-sanctioned affair occurs, it is described as infidelity and may be experienced as adultery, or a betrayal both of trust and integrity, even though to most people it would not be considered "illicit".

When a romantic affair lacks both overt and covert sexual behavior and yet exhibits intense or enduring emotional intimacy it may be referred to as an emotional affair, platonic love, or a romantic friendship.

Extramarital affair
Extramarital affairs are relationships outside of marriage where an illicit romantic or sexual relationship or a romantic friendship or passionate attachment occurs.

An extramarital affair that continues in one form or another for years, even as one of the partners to that affair passes through marriage, divorce and remarriage, could be considered the primary relationship and the marriages secondary to it. This may be serial polygamy or other forms of nonmonogamy.

The ability to pursue serial and clandestine extramarital affairs while safeguarding the secrets and conflict of interest inherent in the practice, requires skill in deception and duplicitous negotiation. Even to hide one affair requires a degree of skill or malicious gaslighting. All these behaviors are more usually called lying. Deception can be defined as the "covert manipulation of perception to alter thoughts, feelings, or beliefs". The presence of deception may indicate the degree to which the deceiver has breached fundamental conditions of fidelity, of reciprocal vulnerability and of transparency. Sometimes these are explicit or assumed pre-conditions of a committed intimate relationship.