Amillennialism is a related term of postmillennialism.

In christianity terms the difference between postmillennialism and amillennialism

is that postmillennialism is an interpretation of the Book of Revelation where Christ's second coming will be after the "Millennium", a Golden Age or era of prosperity and dominance of the Christianity while amillennialism is a view in Christian eschatology that rejects the claimed future thousand-year physical reign of Jesus Christ on the earth, in opposition to premillennial and some postmillennial views of the Book of Revelation, chapter 20, claiming instead that the number of years in Revelation 20 is a symbolic number and that Christ's eventual physical reign will be permanent.