Should Christians Keep the Sabbath?, page-83

Prophecy is an inspired message, whether a revelation of divine will or the proclamation of it. Prophecy may be an inspired moral teaching, an expression of a divine command or judgment, or a declaration of something to come.

(2 Peter 1:20, 21) For you know this first, that no prophecy of Scripture springs from any private interpretation.  For prophecy was at no time brought by man’s will, but men spoke from God as they were moved by holy spirit.

So a prophecy may or may not be to do with the future. To prophesy is a verb, whereas prophecy is a noun.To prophesy is the act of uttering a prophecy.