Infidelity is commonly defined as a breach of an agreed expectation of exclusivity within an intimate partnership. That agreement can be explicit or implicit, sexual or emotional. When a partner forms a sexual or romantic relationship outside the agreed boundaries, many people and cultures describe this as infidelity. The term covers single encounters, ongoing secret sexual relationships, and intense emotional involvements that undermine the primary partnership.

Forms and characteristics

Infidelity takes multiple forms and its meaning depends on the partners' expectations. Typical categories include:

  • Sexual infidelity: physical sexual contact with someone outside the relationship.
  • Emotional infidelity: developing an intimate bond, sharing romantic feelings or confidences with another person in ways that displace the primary partner.
  • Online and virtual infidelity: prolonged messaging, sexualized exchanges, dating apps, secret social media contacts, or virtual relationships that erode intimate trust.
  • Consensual non‑monogamy: arrangements such as polyamory or open relationships where outside relationships are permitted by agreement and therefore not considered cheating.

Prevalence and research considerations

Estimates of how common infidelity is vary widely with method, time period and culture. Mid‑20th century research, including the Kinsey reports, reported substantial rates of extra‑marital sexual activity, with higher reported rates among men than women. More recent surveys show differing rates depending on definitions (sexual contact vs. emotional involvement), sample selection, and social desirability bias. Technology and changing norms have also influenced reported patterns over recent decades.

Societies respond differently to infidelity. In some jurisdictions and traditions, adultery is treated as a legal or moral offense and can be grounds for divorce, social sanctions or criminal penalties. In other places it is treated as a private family matter. Religious teachings across many faiths address unfaithfulness as a moral issue and shape community attitudes and responses. Legal definitions vary: some use the narrower term "adultery" for married persons, while "infidelity" is a broader social concept.

Causes and risk factors

Causes of infidelity are complex and rarely reducible to a single factor. Contributing elements can include dissatisfaction in the relationship, unmet emotional or sexual needs, opportunity, personality traits (such as impulsivity), attachment patterns, life transitions, substance use, and workplace or social environments that facilitate contact with others. Intentional choices, rather than pathology, also underlie many instances of cheating.

Consequences and impacts

Consequences can affect emotional well‑being, relationship stability, family life and public reputation. Common outcomes include loss of trust, intense emotional distress, separation or divorce, and practical effects related to co‑parenting and finances. Infidelity can also increase health risks, for example transmission of sexually transmitted infections, when sexual contact occurs without protection. Children in affected families may experience stress, though outcomes vary widely with context and support.

Responses, repair and prevention

Partners respond to discovery of infidelity in many ways: confrontation, ending the relationship, seeking couple or family therapy, negotiating new boundaries, temporary separation, or mutually agreed changes such as opening the relationship. Professional counseling can assist with disclosure, rebuilding trust, and addressing underlying issues. Preventive strategies include clear communication of expectations, regular relationship check‑ins, setting boundaries about online behavior, and seeking help for relationship difficulties before breaches occur.

Distinctions and ethical considerations

Important distinctions include secretive cheating versus consensual non‑monogamy, emotional versus physical betrayal, and cultural or legal definitions of adultery. Ethical discussions emphasize consent, transparency, and respect for agreed boundaries. When partners have different expectations, misunderstandings about fidelity are common and can lead to perceived betrayal.

For introductory information on agreed exclusivity and sexual norms see sexual exclusivity resources. Historical research on extra‑marital patterns is often discussed in summaries of the Kinsey reports. Religious perspectives that address unfaithfulness appear across traditions; consult materials on religion and morality for context. Legal frameworks and the question of criminalization or civil remedies vary by country; see general guides on law and adultery for jurisdictional differences.