apistos describes people or a generation marked by unbelief, and once something regarded as unbelievable.

The term most often identifies people, groups, or a generation marked by unbelief, frequently set beside believers or faithfulness; in Acts 26:8 it instead characterizes the claim that God raises the dead as something considered unbelievable.

1. People or groups marked by unbelief · dominant

   The adjective identifies individuals and groups in contrast with believers or faithfulness: in John 20:27 the APB renders the instruction to Thomas, “do not be unbelieving but faithful,” and in 2 Corinthians 6:15 it renders a contrast between “a believer” and “an unbeliever.” In 1 Corinthians 7:12 the term describes a wife in a mixed marriage, while Matthew 17:17 addresses an “unbelieving and perverted generation.”

   John 20:272 Corinthians 6:151 Corinthians 7:121 Corinthians 7:141 Corinthians 14:23Matthew 17:17
2. Regarded as unbelievable · rare

   In Acts 26:8, the nominative singular neuter form characterizes the question of God raising the dead; the APB renders the clause, “Why is it considered unbelievable among you that God raises the dead?”

   Acts 26:8

In the Anselm Project Bible: Across the verses, the APB commonly uses “unbeliever” or “unbelieving,” while it uses “faithless” for the addressed generation and “unbelievable” in Acts 26:8. These are renderings of whole translated clauses, not definitions.