The Greek antichristos (ἀντίχριστος) is a compound of anti (against, or in place of) + Christos (Christ/Anointed One). The word can mean both "against Christ" (direct opposition) and "instead of Christ" (false replacement). This double meaning is theologically significant: the antichrist both opposes the true Christ and sets himself up as a substitute. The term appears only in John's epistles (1 John 2:18,22; 4:3; 2 John 1:7) and is not used in Revelation, which uses different imagery.
John's use of antichristos is carefully distinguished from popular eschatological speculation. He writes "as you have heard that antichrist is coming, so now many antichrists have come" (1 John 2:18) — establishing that "the antichrist" is both a coming individual and an already-present spirit. The spirit of antichrist (1 John 4:3) is defined specifically as denying that Jesus Christ has come in the flesh — a Christological error that strikes at the incarnation. Every teaching system that denies the true humanity and deity of Christ operates in the spirit of antichrist. John's focus is not calendar speculation but doctrinal vigilance: the community must test every spirit and hold fast to apostolic Christology.