(Old English: a prefix meaning before in place, rank, or time; in advance)

foreteller (s) (noun), foretellers (pl)
A person who divines events in the future as if by magical powers: In some of the Greek tragedies, the foreteller often used smoke and supernatural words to predict the outcomes of heroic battles.
foretelling (s) (noun), foretellings (pl)
Something that is predicted beyond the laws of nature or normal human understanding: The foretelling of the outcome of the election by the columnist of the newspaper in the city was remarkably accurate.
forethink (verb), forethinks; forethought; forethinking
To mentally consider or to plan in advance: Before Irene goes shopping, she always forethinks about which stores have the best bargains.
forethought (s) (noun), forethoughts (pl)
The exercise of good judgment or common sense in practical matters: People need forethoughts to stay within in their budgets and not to buy more things than they really need.
forethoughtful (adjective), more forethoughtful, most forethoughtful
Characterizing a person who or an animal which plans for the future: The red squirrel in Mary's backyard appears to be more forethoughtful than the other squirrels because it is hiding more nuts for the winter months.
foretoken (s) (noun), foretokens (pl)
A sign of something to come: A foretoken is a phenomenon that serves as a warning of some future good or evil condition.
forewarn (verb), forewarns; forewarned; forewarning
To notify others in advance of imminent dangers or risks: The flashing road signs were placed near the construction site to forewarn drivers of possible harm or injury and encouraging them to slow down and to avoid accidents.
forewarner (s) (noun), forewarners (pl)
An individual or device which is to caution or alert others to potentially risky situations: Marjory's friend, Jake, was one year ahead of her at school and he was her forewarner about the complexity of the upcoming math examinations.
forewarning (s) (noun), forewarnings (pl)
Advanced information of an impending response: Walter had ample forewarning of the reception his report would receive.
forewarning (adjective), more forewarning, most forewarning
Relating to someone who informs others in advance of an impending or possible danger, problem, or of other unpleasant situations: Tim's teacher spoke decisively in the most forewarning manner that cheating on the final exam would not be tolerated.