Definition of epact in English:

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Pronunciation: /ˈēpakt/


[in singular]
1The number of days by which the solar year differs from the lunar year.
1.1The number of days into the moon’s phase cycle at the beginning of the solar (calendar) year.


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'.

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Syllabification: e·pact

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