The study of movements and relative positions of celestial bodies interpreted as having an influence on human affairs and the natural world. Ancient observers of the heavens developed elaborate systems of explanation based on the movements of the sun, moon, and planets through the constellations of the zodiac, for predicting events and for casting horoscopes. By 1700 astrology had lost intellectual credibility in the West, but continued to have popular appeal. Modern astrology is based on that of the Greeks, but other systems are extant, e.g. that of China.
The term (in full natural astrology) originally denoted the practical uses of astronomy, applied in the measurement of time and the prediction of natural phenomena. The commonest sense today (in full judicial astrology, relating to human affairs) dates from the mid 16th century.
The word is recorded from late Middle English, and comes ultimately (via Old French and Latin) from Greek astron ‘star’.