Infidelity is literally a breach of faith and occurs in a number of contexts (e.g., in religious contexts). That referred to here is also called
cheating - 'any violation of the mutually agreed-upon rules or boundaries of a relationship'. What constitutes an act of infidelity varies between and within
cultures, it does not depend on the presence of sexual behaviour. Even within a close relationship people may have very different ideas and perceptions of infidelity - see Blumstein. A man cheated on by his wife is referred to as a
cuckold but no equivalent word exists for a woman cheated on by her partner. The term describes a married man whose wife has sex with other men.
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INCREDULITÀ. MISCREDENZA. INFEDELTÀ