un doubtful (adjective) certain: confident
Sinonime: assertive,
assured, believing,
calm, cocksure,
convinced,
positive, questionless,
sanguine,
satisfied,
secure, self-confident,
sure,
unconcerned, undisturbed, undoubtful, undoubting, unperturbed, untroubled
Antonime: doubtful, doubting,
hesitant,
uncertain, unconfident,
unsure