Definition of equant in US English:



  • (in the Ptolemaic system) an imaginary circle introduced with the purpose of reconciling the planetary movements with the hypothesis of uniform circular motion.

    • ‘But Ptolemy was not trying, when he devised the equant, to offer a mechanical account of why the planets moved as they did.’
    • ‘If you had asked Aristotle or Ptolemy to explain how planets move, you would have got a lecture on epicycles and equants.’
    • ‘Gingerich noted ‘the majority of sixteenth-century astronomers thought eliminating the equant was Copernicus' big achievement.’’
    • ‘While the epicycle is moving at a uniform rate with respect to the equant, it does not move at a uniform rate with respect to the centre of the deferent or even with respect to the Earth.’
    • ‘When the intricacies of epicycles, deferents and equants were explained to him Alfonso ‘the Wise’ is said to have remarked that if the Almighty had consulted him on the matter, he would have recommended something a little simpler…’


  • (of a crystal or particle) having its different diameters approximately equal, so as to be roughly cubic or spherical in shape.

    • ‘Both samples consist of fine-grained calcite with elongated or equant shapes.’
    • ‘Doubly terminated, transparent, colorless equant crystals of classic Herkimer ‘diamond’ habit are locally common.’
    • ‘A few outstanding composite specimens were recovered, with crude dendritic copper intergrown with one or two large, single, equant crystals.’
    • ‘It typically occurs as transparent flattened crystals, as small equant crystals, as intergrown masses of small lustrous crystals, and occasionally as stout or elongated twinned crystals.’
    • ‘This large (about 5 meters in diameter) equant vein has a distinct concentric zonation.’


Mid 16th century: from Latin aequant- ‘making equal’, from the verb aequare.