astrology, n.

In ancient Greek ἀστρολογία   and ἀστρονομία   were effectively synonymous, both words denoting the science of celestial objects. Influenced by the Egyptians and the Chaldeans, the Greeks of the Hellenistic period began to make calculations and predictions on the basis of astronomical observations, and the word ἀστρολογία   came to be used in this sense. In Latin astrologia   is used earliest (in Varro, 1st cent. b.c.) and predominantly to denote the science of celestial objects. Astronomia   first appears a little later (in Seneca, 1st cent. a.d.). The first author who attempts a semantic distinction between the two Latin words is Isidore (a636). Isidore ( Origines 3. 27) defines astronomia   as incorporating the positions and motions of planets and stars; he distinguishes between astrologia naturalis  , the study of celestial phenomena, and astrologia superstitiosa  , the practice of divination and predictions based on observations of celestial phenomena. In medieval French, and likewise in Middle English, astronomie  astronomy n.   is attested earlier, and originally covered the whole semantic field of the study of celestial objects, including divination and predictions based on observations of celestial phenomena. In early use in French and English, astrologie  astrology n.   is generally distinguished as the ‘art’ or practical application of astronomy to mundane affairs, but there is considerable semantic overlap between the two words (as also in other European languages). With the rise of modern science from the Renaissance onwards, the modern semantic distinction between astrology n.   and astronomy n.   gradually developed, and had become largely fixed by the 17th cent. (although compare sense 2   for later exceptions, and likewise later examples at astronomy n. 2). The word is not used by Shakespeare. With natural astrology at sense 1a   compare post-classical Latin astrologia naturalis   (a636 in Isidore). With judicial astrology   compare Middle French, French astrologie judiciaire (1533).