Definition of Almagest in US English:



the Almagest
  • 1An influential treatise on astronomy written by the Greek astronomer and geographer Ptolemy in the second century AD.

    • ‘Finally, the translation of Ptolemy's Almagest furnished important astronomical material.’
    • ‘But once they had translated Ptolemy's Almagest, they developed astronomy so quickly that their mark is found at every step.’
    • ‘Menelaus's work formed the basis for Ptolemy's numerical solutions of spherical astronomy problems in the Almagest.’
    • ‘Ptolemy's Almagest was a complete theory, but it involved applying a different mathematical formula for the motion of each planet and therefore did not really represent an overall unifying system.’
    • ‘Ptolemy's Almagest was one of the works which Arabic scientists studied intently.’
    1. 1.1 (in the Middle Ages) any celebrated textbook on astrology and alchemy.


Late Middle English: from Old French almageste, based on Arabic, from al ‘the’ + Greek megistē ‘greatest (composition)’.