• synonyms


  1. the difference in days between a solar year and a lunar year.
  2. the number of days since the new moon at the beginning of the calendar year, January 1.
Show More

Origin of epact

1545–55; < Late Latin epacta < Greek epaktḗ, noun use of feminine of epaktós added, equivalent to ep- ep- + ag(ein) to lead + -tos verbid suffix
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for epact

Historical Examples

  • The Epact is the number of days which must be added to a lunar year to complete a solar year.

    Time and Time-Tellers

    James W. Benson

  • The epact thus continues to vary until at the end of nineteen years the new moons return as at first.

    Time Telling through the Ages

    Harry Chase Brearley

  • Thus we have the epact, or age of the Calendar moon at the beginning of the year.

  • Thus, when the epact is 17, the new and full moons of March fall on the 13th and 28th.

  • During those few and sombre days which represented the epact of the dying year, Martin Grimbal returned to Chagford.

    Children of the Mist

    Eden Phillpotts

British Dictionary definitions for epact


  1. the difference in time, about 11 days, between the solar year and the lunar year
  2. the number of days between the beginning of the calendar year and the new moon immediately preceding this
  3. the difference in time between the calendar month and the synodic month
Show More

Word Origin

C16: via Late Latin from Greek epaktē, from epagein to bring in, intercalate, from agein to lead
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for epact


1550s, "number of days by which the solar year exceeds a lunar one of 12 moons;" also "number of days into the moon on which the solar year begins;" from French épacte (12c.), from Late Latin epacta "an intercalary day," from Greek epaktos, literally "brought in, inported," verbal adjective of epagein "to intercalate, add, bring forward," from epi "on" (see epi-) + agein "to bring, to lead" (see act (v.)).

Show More
Online Etymology Dictionary, © 2010 Douglas Harper