[lu.na.tion] n [ME lunacioun, fr. ML lunation-, lunatio, fr. L luna] (14c): the period of time averaging 29 days, 12 hours, 44 minutes, and 2.8 seconds elapsing between two successive new moons
LUNATION
Meaning of LUNATION in English
Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012