Bible Greek and Hebrew Dictionaries combined for Word Studies
Genesis Chapter 1
unbelief 0543 # apeitheia {ap-i'-thi-ah}; from 545; disbelief (obstinate and rebellious): -- disobedience, {unbelief}.
unbelief 0570 # apaistia {ap-is-tee'-ah}; from 571; faithlessness, i.e. (negatively) disbelief (lack of Christian faith), or (positively) unfaithfulness (disobedience): -- {unbelief}.