Apotelesmatika or "Astrological Outcomes" is the original Greek version of a book later translated into Latin as , and thence into Latin as the Tetrabiblos, or "Four Books". The Tetrabiblos is an extensive and continually reprinted treatise on the ancient principles of horoscopic astrology in four books (Greek tetra means "four", biblos is "book"). That it did not quite attain the unrivaled status of the Almagest was perhaps because it did not cover some popular areas of the subject, particularly electional astrology (interpreting astrological charts for a particular moment to determine the outcome of a course of action to be initiated at that time,) and medical astrology.