Definition of ephemeris in English:

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Pronunciation: /ɪˈfɛm(ə)rɪs/

noun (plural ephemerides /ˌɛfɪˈmɛrɪdiːz/)

Astronomy & Astrology
A table or data file giving the calculated positions of a celestial object at regular intervals throughout a period: you can compute an ephemeris for any comet that is discovered and plot an accurate finder chart
More 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.


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

For editors and proofreaders

Line breaks: ephem|eris

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