1: ἀπιστία
(Strong's #570 — Noun Feminine — apistia — ap-is-tee'-ah )

"unbelief" 12 times, but see BELIEF , C, Note (2) for references.

2: ἀπείθεια
(Strong's #543 — Noun Feminine — apeitheta — ap-i'-thi-ah )

is always rendered "disobedience" in the RV; in Romans 11:30,32 and Hebrews 4:6,11 , AV, "unbelief." See DISOBEDIENCE , A, No. 1.