ephemeris

UK: /ɪˈfɛmərɪs/ US: (i fem′ər is)

Inflections of 'ephemeris' (n): npl: ephemerides

WordReference Random House Unabridged Dictionary of American English © 2025

e•phem•er•is  (i fem′ər is), n., pl. e•phe•mer•i•des 

(ef′ə mer′i dēz′). 
1. Astronomy a table showing the positions of a heavenly body on a number of dates in a regular sequence.
2. Astronomy an astronomical almanac containing such tables.
3. [Archaic.] an almanac or calendar.

• Greek ephēmerís diary, account book, derivative of ephé̄meros; see ephemeral
• Latin ephēmeris day book, diary
• 1545–55

Collins Concise English Dictionary © HarperCollins Publishers::

ephemeris / ɪˈfɛmərɪs/ noun ( ephemerides / ˌɛfɪˈmɛrɪˌdiːz/)

1. a table giving the future positions of a planet, comet, or satellite

Etymology: 16th Century: from Latin, from Greek: diary, journal; see ephemeral