An omen is a phenomenon that is believed to foretell the future, often signifying the advent of change. It was commonly believed in ancient times, and still believed by some today, that omens bring divine messages from the gods.
Examples of omens from the Nuremberg Chronicle (1493): natural phenomena and unnatural births.
Manuscript of the mid-nineteenth century, possibly of Sgaw Karen origin, shows various appearances in the sun, the moon, clouds, etc., and indicates the primarily bad omens these appearances foretell. Explanations in English were added to this manuscript by a nineteenth-century American missionary.
Halley's Comet's appearance in 1066 was recorded on the Bayeux Tapestry. ISTI MIRANT STELLA literally means "These ones are looking in wonder at the star". National Geographic translated it in a 1966 article about the tapestry as "These men wonder at the star".
A prediction or forecast is a statement about a future event or about future data. Predictions are often, but not always, based upon experience or knowledge of forecasters. There is no universal agreement about the exact difference between "prediction" and "estimation"; different authors and disciplines ascribe different connotations.
The Old Farmer's Almanac is famous in the US for its (not necessarily accurate) long-range weather predictions.
Asklepios and Hippocrates bookend the façade of the Royal College of Physicians of Edinburgh, statuary by Alexander Handyside Ritchie (1804-1870)
