Definitions

1. noun

A table of the positions of celestial bodies, especially the sun, moon, and planets, at regular intervals, used in astronomy for navigation and timekeeping.

“The astronomer used the ephemeris to calculate the exact time of the planetary alignment.”

2. noun

A period of time for which something is planned or scheduled.

“The event’s ephemeris was only a few days, giving organizers a tight deadline to prepare.”