To predict something is to tell in advance what will happen. This verb often (but not always) implies calculation, knowledge, or shrewd inference from facts or experience, as in the case of astronomers who predict an eclipse. The verb prognosticate deals primarily in signs and omens. A thing, such as the presence or absence of a certain groundhog’s shadow, can prognosticate, or presage, something (the estimated time of arrival for spring). Similarly, a person can prognosticate, or foretell, a future event from present indications or signs. The related word prognosis is used in medicine to talk about the probable course and outcome of a disease, especially of the chances of recovery.