The terms astronomy, astrophysics and astrology are often used synonymously, even though they have very different meanings.
Astronomy Versus Astrophysics
The difference between astronomy (literally star law in Greek) and astrophysics (derived from the words star physics) comes in what they two disciplines are trying to accomplish.
Astronomy seeks to determine the laws that govern the motion and origins of the heavenly bodies (stars, planets, galaxies, etc.). Whereas astrophysicists are more concerned with studying the physical processes that lead to the creation of stars and galaxies, as well as learning what drives their emission and evolution. The two are definitely interrelated, but are clearly trying to answer different questions.
Despite this, the two terms have become somewhat synonymous in recent years. This can be attributed to the fact that most astronomers receive the same training as astrophysicists, including the completion of a graduate program in physics (although there are several very good pure astronomy programs still taught throughout the country).
More importantly though, it is becoming increasingly difficult to address a purely astronomical problem; much of the work done in the field requires the application of astrophysical principles and theories. So while there are, strictly speaking, differences in definitions of the two terms, in application it is difficult to distinguish between them.
Astronomy Versus Astrology
Astrology (literally star study in Greek) is a whole different field of study all together. So much so, that it is mostly regarded as a pseudoscience.
Astrologists believe that the relative positions of celestial bodies can give us information about people’s individual characteristics, affairs and future. While astrology has no scientific basis, it did have a foundational role in the development of astronomy and various historical events, as it was astrologists that first began peering into the heavens centuries ago.
