From Longman Dictionary of Contemporary Englishnot a whitnot a whitold-fashionedNONE/NOTHING not at all Sara had not changed a whit. → whit
Examples from the Corpus
not a whit• I know that his intervention was well meant and had not a whit of political mischief about it.• The patients' needs don't seem to matter a whit to the hospital.• For I suppose I was not a whit behind the very chiefest apostles. 