Definition of gnomon in English:



  • 1The projecting piece on a sundial that shows the time by the position of its shadow.

    • ‘To ensure that the sundial registered roughly the correct time all the year round the gnomon had to be set at exactly the correct angle.’
    • ‘The problem is that the gardeners have been caught on the gnomon of their own sundial.’
    • ‘He placed a pole perfectly upright in the ground to make a simple sundial, or gnomon.’
    • ‘He also probably introduced the gnomon (a perpendicular sun-dial) into Greece and erected one in Sparta.’
    1. 1.1Astronomy A structure, especially a column, used in observing the sun's meridian altitude.
      • ‘He is also said to have constructed a armillary sphere, a water clock, and a bronze gnomon, a pointer whose shadow gives the time of mid-day.’
      • ‘The text measures the positions of the heavenly bodies using shadow gauges which are also called gnomons.’
      • ‘It is an astronomy text, showing how to measure the positions of the heavenly bodies using shadow gauges which are also called gnomons, but it contains important sections on mathematics.’
      • ‘Pergolas, open steel stairs, lattices and wooden blinds all act as shadow-casters and gnomons.’
      • ‘The simplest astronomical instruments was the gnomon, nothing other than a stick which was erected and the length of its shadow measured.’
  • 2Geometry
    The part of a parallelogram left when a similar parallelogram has been taken from its corner.

    • ‘Revolve the gnomon about its vertex and it can draw a circle; combine two gnomons and they form a square.’
    • ‘When the gnomon is turned up, it can measure height; when it is turned over, it can measure depth and when it lies horizontally it can measure distance.’


Mid 16th century: via Latin from Greek gnōmōn ‘indicator, carpenter's square’ (related to gignōskein ‘know’).