Pre-indication, also called a warning sign, is a sign or signal that something is about to happen or change significantly. Synonyms for pre-indication include foreshadowing, harbinger, portent, omen, augury, prediction, forecast, and precursory sign. Foreshadowing refers to the use of hints or clues to suggest what will happen in the future. Harbinger and portent both suggest that something important or ominous is on the horizon. Omens are believed to foretell future events, while auguries are signs of favorable or unfavorable outcomes. A prediction and forecast both indicate what will likely happen in the future, while a precursory sign is a signal that something is about to happen soon.