Epicycles are circles within circles, a term used in astronomy to describe the complex paths of celestial objects as observed from earth. There are various synonyms for the word "epicycles," including "orbits," "cycles," and "revolutions." Other related terms include "eccentricities," which describe the deviations from perfect circles, and "ellipses," which are oval shapes that celestial objects take during their orbits. In modern astronomy, the term "epicycles" is rarely used, as our understanding of celestial mechanics has evolved to more accurate models and theories. Nonetheless, the concept of epicycles remains an important part of history and the evolution of scientific thought.