unfaithfulness
🇺🇸
/ʌnˈfeɪθflnəs/
🇬🇧
/ʌnˈfeɪθflnəs/
Being dishonest in a romantic relationship by having a sexual relationship with someone other than your partner.
The discovery of his unfaithfulness broke her heart.
發現他的背叛讓她心碎。