不忠 in inglese:

The cat is a symbol of infidelity.

I never engaged myself in any act of infidelity

infidelity among pairs living in large groups became more risky than ever

Her husband's infidelity was the reason for their separation.

Among other common reasons for breaking up are housing problems, infidelity, negligence towards familiy duties, a conflict of values and, above all, alcohol abuse which riuns family life and leads to quarrels and acts od violence.

He'd broken her heart with his infidelity.

She never forgave him the infidelity and held it over him every chance that she got.

Day after day the tabloids titillated the public with lurid details about the president's marital infidelity.