Prognosis (Greek πρόγνωση - literally fore-knowing, foreseeing) is a medical term for predicting the likely outcome of an illness, often involving a detailed description.
When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because previous research found that this proportion of patients died. However, it is much harder to translate this into a prognosis for an individual patient: additional information is needed to determine whether a patient belongs to the 45% who will succumb, or to the 55% who survive.
A complete prognosis includes the expected duration, the function, and a description of the course of the disease, such as progressive decline, intermittent crisis, or sudden, unpredictable crisis.