[ ee-pakt ]
/ ˈi pækt /


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

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. 2019

Examples from the Web for epact

British Dictionary definitions for epact


/ (ˈiːpækt) /


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

Word Origin for epact

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