Source : Webster's Revised Unabridged Dictionary (1913)

Ephemeris \E*phem"e*ris\, n.; pl. {Ephemerides}. [L., a diary,
   Gr. ?, also, a calendar, fr. ?. See {Ephemera}.]
   1. A diary; a journal. --Johnson.

   2. (Anat.)
      (a) A publication giving the computed places of the
          heavenly bodies for each day of the year, with other
          numerical data, for the use of the astronomer and
          navigator; an astronomical almanac; as, the ``American
          Ephemeris and Nautical Almanac.''
      (b) Any tabular statement of the assigned places of a
          heavenly body, as a planet or comet, on several
          successive days.

   3. (Literature) A collective name for reviews, magazines, and
      all kinds of periodical literature. --Brande & C.

Source : WordNet®

ephemerides
     See {ephemeris}

ephemeris
     n : an annual publication containing astronomical tables that
         give the positions of the celestial bodies throughout the
         year; "today computers calculate the ephemerides"
     [also: {ephemerides} (pl)]