Infidelity is breaking a promise to remain faithful to a romantic partner, whether that promise was a part of marriage vows, a privately uttered agreement between lovers, or an unspoken assumption. As unthinkable as the notion of breaking such promises may be at the time they are made, infidelity is common, and when it happens, it raises thorny questions: Should you stay? Can trust be rebuilt? Or is there no choice but to pack up and move on?

For the adulterer, infidelity can be exciting and seductive, conferring feelings of renewal, rejuvenation, and joy. Infidelity is a betrayal, but it isn’t necessarily the end of love; cheating occurs even in happy relationships. The partner being betrayed may feel confusion, anger, doubt, pain, and heartbreak.

Most people know the costs of cheating in a relationship, particularly in a marriage. Betrayal can lead to divorce and parental disruption, and infidelity is a predictor of depression, anxiety, and domestic violence. Yet many stray anyway, prompting the question: Why? In surveys of individuals who have cheated, falling out of love, seeking variety, and feeling neglected were the most commonly cited reasons, followed by situational forces, a desire to raise self-esteem, and anger with a partner.

Men have always been more likely than women to cheat, or at least to report having done so, but researchers have noticed a shift in recent years: 16% of adults, about 20% of men, and 13% of women report that they’ve had sex with someone other than their spouse while married. But among adults under 30 who have been married, 11% of women say having committed infidelity, as opposed to 10% of men.

The line between innocent flirtation and romantic betrayal is often elastic, and many couples face conflict because partners do not share the same definition of cheating. For some, anything short of sexual contact with someone else is acceptable; for others, any attention to a potential rival is unforgivable.

The term “micro-cheating” refers