Definition of epact in English:

epact

noun

  • 1[in singular] The number of days by which the solar year differs from the lunar year.

    1. 1.1 The number of days into the moon's phase cycle at the beginning of the solar (calendar) year.

Origin

Mid 16th century (denoting the age of the moon in days at the beginning of the calendar year): from French épacte, via late Latin from Greek epaktai (hēmerai) intercalated (days) from epagein bring in from epi in addition + agein bring.

Pronunciation:

epact

/ˈēpakt/