The Greek noun agnoia means ignorance or lack of knowledge — specifically, willful or culpable ignorance rather than mere uninformed innocence. It occurs 4 times in the New Testament and is the corresponding noun to agnoeo (to not know, be ignorant). The related agnoema (sin of ignorance) appears in Hebrews.
Agnoia in the New Testament is not the innocent unknowing of a child but the culpable blindness of those who have had opportunity to know better. Acts 17:30 is the key text: 'In the past God overlooked such ignorance (agnoia), but now he commands all people everywhere to repent.' The coming of Christ ended the era of relative ignorance — now all stand accountable to the revealed gospel. Peter similarly writes that Christians must not 'conform to the evil desires you had when you lived in ignorance' (1 Peter 1:14). This theological use of agnoia establishes a before-and-after: before Christ, partial ignorance; after Christ, full revelation and full accountability.