Father Derek's Reply:
" the Greek word “apocalypsis,” which is the first word of the Book of Revelation, means “revelation” - literally, “uncovering.” It is from the preposition “apo” (“away from”) and the verb “kalypso” (“I cover”).
So there really is no difference between “revelation” and “apocalypse.” Of course, part of content of the revelation or “apocalypsis” of the book is the catastrophes of the last days. Perhaps this is why in English and Spanish, the word “apocalypse” or “apocalipsis” also has the sense of disaster or end of the world.
But in Greek, the word just means revelation."