FROM STRONG’S GREEK DICTIONARY (1890)

Strong’s Greek Dictionary (1890) — public domain, printed whole.

apistia ἀπιστία — ap-is-tee'-ah — from 571; faithlessness, i.e. (negatively) disbelief (lack of Christian faith), or (positively) unfaithfulness (disobedience):--unbelief.

see GREEK for 571