Word family noun faith faithfulness ≠ unfaithfulness faithful faithlessness adjective faithful ≠ unfaithful faithless adverb faithfully ≠ unfaithfully
From Longman Dictionary of Contemporary Englishunfaithfulun‧faith‧ful /ʌnˈfeɪθfəl/ ●○○ adjective SYSEX/HAVE SEX WITHsomeone who is unfaithful has sex with someone who is not their wife, husband, or usual partner → infidelityunfaithful to Geoff had been unfaithful to her on many occasions. —unfaithfully adverb —unfaithfulness noun [uncountable]Examples from the Corpus
unfaithful• But it is not at all clear why the female is so often unfaithful.• But third, women are sometimes unfaithful.• Jeff promised he'd never be unfaithful again.• Claudio is the unfaithful, deceitful { friend } who leads Leonardo astray into drinking, gambling and having romantic affairs.• They are building up alternative relationships and are more likely to be unfaithful if the marriage is going badly.• Why do women stay with unfaithful partners?• All the time she wildly imagines him being unfaithful to her in a thousand trivial ways.• He had never once been unfaithful to her nor she to him, he would gamble, until now.• He accused me of being unfaithful to him.• Later I found out that my husband was being unfaithful to me.• Was it possible to be unfaithful yet still love your wife?unfaithful to• Nell was shocked to discover her father had been unfaithful to her mother. 