Metonic cycle

UK: /mɪˈtɒnɪk/ US: (mi ton′ik)

WordReference Random House Unabridged Dictionary of American English © 2026

Me•ton′ic cy′cle  (mi ton′ik), [Astron.]

1. a cycle of 235 synodic months, very nearly equal to 19 years, after which the new moon occurs on the same day of the year as at the beginning of the cycle with perhaps a shift of one day, depending on the number of leap years in the cycle.

• 1880–85; named after Meton, 5th-century b.cognate withAthenian astronomer; see -ic

Collins Concise English Dictionary © HarperCollins Publishers::

Metonic cycle / mɪˈtɒnɪk/ noun

1. a cycle of nearly 235 synodic months after which the phases of the moon recur on the same days of the year
   See also golden number

Etymology: 17th Century: named after Meton, 5th-century bc Athenian astronomer