Word family noun truth ≠ untruth truthfulness adjective true ≠ untrue truthful ≠ untruthful adverb truly truthfully ≠ untruthfully true
From Longman Dictionary of Contemporary Englishuntruthfulun‧truth‧ful /ʌnˈtruːθfəl/ adjective DISHONESTdishonest or not true —untruthfully adverbExamples from the Corpus
untruthful• Most of what they do and others do to them is illegal, deceitful and untruthful.• Much better to be untruthful and leave Laura thinking that but for a migraine, they might have spent the night together.• In this, of course, the untruthful organization is totally mistaken. 