'Sign' in the Bible

A great sign appeared in heaven: a woman clothed with the sun, and the moon under her feet, and on her head a crown of twelve stars;

Then another sign appeared in heaven: and behold, a great red dragon having seven heads and ten horns, and on his heads were seven diadems.

Then I saw another sign in heaven, great and marvelous, seven angels who had seven plagues, which are the last, because in them the wrath of God is finished.