Definition of ephemeris in English:

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Pronunciation: /əˈfem(ə)rəs/

noun (plural ephemerides /-ərədēz/)

Astronomy & Astrology
1A table or data file giving the calculated positions of a celestial object at regular intervals throughout a period.
Example sentences
  • Timing an occultation to a fraction of a second allows the observed location to be referenced against the predicted position from the computed ephemeris, perhaps leading to an update.
  • It's not commonly realised that there is a strong notional element in some of the times so confidently listed in the ephemeris, as will become clear if you compare the times given for aspects of the major planets in different ephemerides.
  • Global networks of tracking stations produce the observations that make generation of the precise ephemerides possible.
1.1A book or set of such tables or files.
Example sentences
  • He purchased an ephemeris.
  • Alternatively, you can use an ephemeris to look up the daily positions, but these are usually more expensive and not really worth buying unless you are going to be tracking other astrological things too.
  • The first of his long-running annual ephemerides appeared in 1655 and the following year he published An Emendation of Hartgil's Astronomical Tables.


Early 16th century: from Latin, from Greek ephēmeros 'lasting only a day'.

For editors and proofreaders

Syllabification: e·phem·er·is

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