IPA: /ˈdaʊt.fəl.nəs/
KK: /ˈdaʊt.fəl.nəs/
The condition of being unsure or having uncertainty about something.
Her doubtfulness about the project made her hesitant to proceed.
Doubtfulness → It is formed from "doubt" (from Old French *douter*, meaning to fear or be uncertain) and "-fulness" (meaning the state of being full of). The word "doubtfulness" means the state of being full of doubt or uncertainty.
Think of being 'full of uncertainty' — 'doubt' means uncertainty, and '-fulness' indicates a state of being.